same result:
Server

{
  "derp": {
    "severity": "ok",
    "warnings": [],
    "dismissed": false,
    "healthy": true,
    "regions": {
      "1000": {
        "healthy": true,
        "severity": "ok",
        "warnings": [],
        "region": {
          "EmbeddedRelay": false,
          "RegionID": 1000,
          "RegionCode": "coder_stun_1000",
          "RegionName": "Coder STUN 1000",
          "Nodes": [
            {
              "Name": "1000stun0",
              "RegionID": 1000,
              "HostName": "10.244.5.167",
              "STUNPort": 3478,
              "STUNOnly": true
            }
          ]
        },
        "node_reports": [
          {
            "healthy": true,
            "severity": "ok",
            "warnings": [],
            "node": {
              "Name": "1000stun0",
              "RegionID": 1000,
              "HostName": "10.244.5.167",
              "STUNPort": 3478,
              "STUNOnly": true
            },
            "node_info": {
              "TokenBucketBytesPerSecond": 0,
              "TokenBucketBytesBurst": 0
            },
            "can_exchange_messages": false,
            "round_trip_ping": "",
            "round_trip_ping_ms": 0,
            "uses_websocket": false,
            "client_logs": [],
            "client_errs": [],
            "stun": {
              "Enabled": true,
              "CanSTUN": true,
              "Error": null
            }
          }
        ]
      },
      "999": {
        "healthy": true,
        "severity": "ok",
        "warnings": [],
        "region": {
          "EmbeddedRelay": true,
          "RegionID": 999,
          "RegionCode": "coder",
          "RegionName": "Coder Embedded Relay",
          "Nodes": [
            {
              "Name": "999b",
              "RegionID": 999,
              "HostName": "coder-prod.intranet.mycompany.com",
              "STUNPort": -1,
              "DERPPort": 443
            }
          ]
        },
        "node_reports": [
          {
            "healthy": true,
            "severity": "ok",
            "warnings": [],
            "node": {
              "Name": "999b",
              "RegionID": 999,
              "HostName": "coder-prod.intranet.mycompany.com",
              "STUNPort": -1,
              "DERPPort": 443
            },
            "node_info": {
              "TokenBucketBytesPerSecond": 0,
              "TokenBucketBytesBurst": 0
            },
            "can_exchange_messages": true,
            "round_trip_ping": "524.733µs",
            "round_trip_ping_ms": 0,
            "uses_websocket": false,
            "client_logs": [
              [
                "derphttp.Client.Connect: connecting to https://coder-prod.intranet.mycompany.com/derp",
                "derphttp.Client.Connect: TLS version 0x304",
                "derpclient: got cert coder-prod.intranet.mycompany.com",
                "derpclient: got cert R10",
                "derphttp.Client.Connect: not using fast start",
                "derphttp.Client.Connect: DERP server returned status 101"
              ],
              [
                "derphttp.Client.Connect: connecting to https://coder-prod.intranet.mycompany.com/derp",
                "derphttp.Client.Connect: TLS version 0x304",
                "derpclient: got cert coder-prod.intranet.mycompany.com",
                "derpclient: got cert R10",
                "derphttp.Client.Connect: not using fast start",
                "derphttp.Client.Connect: DERP server returned status 101"
              ]
            ],
            "client_errs": [
              [],
              []
            ],
            "stun": {
              "Enabled": false,
              "CanSTUN": false,
              "Error": null
            }
          }
        ]
      }
    },
    "netcheck": {
      "UDP": true,
      "IPv6": false,
      "IPv4": true,
      "IPv6CanSend": false,
      "IPv4CanSend": true,
      "OSHasIPv6": true,
      "ICMPv4": false,
      "MappingVariesByDestIP": false,
      "HairPinning": null,
      "UPnP": false,
      "PMP": false,
      "PCP": false,
      "PreferredDERP": 999,
      "RegionLatency": {
        "999": 626273
      },
      "RegionV4Latency": {
        "999": 626273
      },
      "RegionV6Latency": {},
      "GlobalV4": "10.244.128.200:56626",
      "GlobalV6": "",
      "CaptivePortal": null
    },
    "netcheck_logs": [
      "netcheck: [v1] measuring ICMP latency of coder (999): no address for node 999b",
      "netcheck: netcheck.runProbe: got STUN response for 1000stun0 from 10.244.128.200:56626 (8b89928cdadcce7871a98631) in 868.917µs",
      "netcheck: netcheck.runProbe: got STUN response for 1000stun0 from 10.244.128.200:56626 (4297f1929e1e4745b94d777a) in 926.862µs",
      "netcheck: netcheck.runProbe: got STUN response for 1000stun0 from 10.244.128.200:56626 (af14d6130529aa3e003e66b8) in 888.68µs",
      "netcheck: [v1] report: udp=true v6=false v6os=true mapvarydest=false hair= portmap= v4a=10.244.128.200:56626 derp=999 derpdist=999v4:1ms"
    ]
  },
  "interfaces": {
    "severity": "ok",
    "warnings": null,
    "dismissed": false,
    "interfaces": [
      {
        "name": "lo",
        "mtu": 65536,
        "addresses": [
          "127.0.0.1/8",
          "::1/128"
        ]
      },
      {
        "name": "eth0",
        "mtu": 1480,
        "addresses": [
          "10.244.128.200/32",
          "fe80::8487:86ff:fe52:1ab2/64"
        ]
      }
    ]
  }
}


Client

p-user@dgt-dev-5dc6797f5-22746:/tmp/passthrough$ coder netcheck
Gathering a network report. This may take a few seconds...

{
  "derp": {
    "severity": "ok",
    "warnings": [],
    "dismissed": false,
    "healthy": true,
    "regions": {
      "1000": {
        "healthy": true,
        "severity": "ok",
        "warnings": [],
        "region": {
          "EmbeddedRelay": false,
          "RegionID": 1000,
          "RegionCode": "coder_stun_1000",
          "RegionName": "Coder STUN 1000",
          "Nodes": [
            {
              "Name": "1000stun0",
              "RegionID": 1000,
              "HostName": "10.244.5.167",
              "STUNPort": 3478,
              "STUNOnly": true
            }
          ]
        },
        "node_reports": [
          {
            "healthy": true,
            "severity": "ok",
            "warnings": [],
            "node": {
              "Name": "1000stun0",
              "RegionID": 1000,
              "HostName": "10.244.5.167",
              "STUNPort": 3478,
              "STUNOnly": true
            },
            "node_info": {
              "TokenBucketBytesPerSecond": 0,
              "TokenBucketBytesBurst": 0
            },
            "can_exchange_messages": false,
            "round_trip_ping": "",
            "round_trip_ping_ms": 0,
            "uses_websocket": false,
            "client_logs": [],
            "client_errs": [],
            "stun": {
              "Enabled": true,
              "CanSTUN": true,
              "Error": null
            }
          }
        ]
      },
      "999": {
        "healthy": true,
        "severity": "ok",
        "warnings": [],
        "region": {
          "EmbeddedRelay": true,
          "RegionID": 999,
          "RegionCode": "coder",
          "RegionName": "Coder Embedded Relay",
          "Nodes": [
            {
              "Name": "999b",
              "RegionID": 999,
              "HostName": "coder-prod.intranet.mycompany.com",
              "STUNPort": -1,
              "DERPPort": 443
            }
          ]
        },
        "node_reports": [
          {
            "healthy": true,
            "severity": "ok",
            "warnings": [],
            "node": {
              "Name": "999b",
              "RegionID": 999,
              "HostName": "coder-prod.intranet.mycompany.com",
              "STUNPort": -1,
              "DERPPort": 443
            },
            "node_info": {
              "TokenBucketBytesPerSecond": 0,
              "TokenBucketBytesBurst": 0
            },
            "can_exchange_messages": true,
            "round_trip_ping": "635.744µs",
            "round_trip_ping_ms": 0,
            "uses_websocket": false,
            "client_logs": [
              [
                "derphttp.Client.Connect: connecting to https://coder-prod.intranet.mycompany.com/derp",
                "derphttp.Client.Connect: TLS version 0x304",
                "derpclient: got cert coder-prod.intranet.mycompany.com",
                "derpclient: got cert R10",
                "derphttp.Client.Connect: not using fast start",
                "derphttp.Client.Connect: DERP server returned status 101"
              ],
              [
                "derphttp.Client.Connect: connecting to https://coder-prod.intranet.mycompany.com/derp",
                "derphttp.Client.Connect: TLS version 0x304",
                "derpclient: got cert coder-prod.intranet.mycompany.com",
                "derpclient: got cert R10",
                "derphttp.Client.Connect: not using fast start",
                "derphttp.Client.Connect: DERP server returned status 101"
              ]
            ],
            "client_errs": [
              [],
              []
            ],
            "stun": {
              "Enabled": false,
              "CanSTUN": false,
              "Error": null
            }
          }
        ]
      }
    },
    "netcheck": {
      "UDP": true,
      "IPv6": false,
      "IPv4": true,
      "IPv6CanSend": false,
      "IPv4CanSend": true,
      "OSHasIPv6": true,
      "ICMPv4": false,
      "MappingVariesByDestIP": false,
      "HairPinning": null,
      "UPnP": false,
      "PMP": false,
      "PCP": false,
      "PreferredDERP": 999,
      "RegionLatency": {
        "999": 1049015
      },
      "RegionV4Latency": {
        "999": 1049015
      },
      "RegionV6Latency": {},
      "GlobalV4": "10.244.5.118:33523",
      "GlobalV6": "",
      "CaptivePortal": null
    },
    "netcheck_logs": [
      "netcheck: [v1] measuring ICMP latency of coder (999): no address for node 999b",
      "netcheck: netcheck.runProbe: got STUN response for 1000stun0 from 10.244.5.118:33523 (2ed1824081c4200d0bf9f3fe) in 419.103µs",
      "netcheck: netcheck.runProbe: got STUN response for 1000stun0 from 10.244.5.118:33523 (2be8763d3faa21987a4f5602) in 413.446µs",
      "netcheck: netcheck.runProbe: got STUN response for 1000stun0 from 10.244.5.118:33523 (d2e5c1325bd87d136fd4d2c7) in 459.776µs",
      "netcheck: [v1] report: udp=true v6=false v6os=true mapvarydest=false hair= portmap= v4a=10.244.5.118:33523 derp=999 derpdist=999v4:1ms"
    ]
  },
  "interfaces": {
    "severity": "ok",
    "warnings": null,
    "dismissed": false,
    "interfaces": [
      {
        "name": "lo",
        "mtu": 65536,
        "addresses": [
          "127.0.0.1/8",
          "::1/128"
        ]
      },
      {
        "name": "eth0",
        "mtu": 1480,
        "addresses": [
          "10.244.5.118/32",
          "fe80::fc5b:4eff:fe2c:9e8/64"
        ]
      }
    ]
  }
}