Cannot Access Applications behind Traefik with Firefox Mobile

Traefik Traefik v3 (latest)
1

I've been struggling with this strange problem for a few weeks now. I set up a Traefik 3 instance on docker and have a few applications running behind it (Navidrome, Heimdall, etc.) with no problems. I can type in the FQDN and hit them all just fine from my various computers. The problem comes into play when I try to access anything by it's FQDN on my Android phone using Firefox Mobile. This is all on my local wifi network and not external (don't have anything exposed to the outside world).

Firefox immediately returns an "Address not found" error when trying to go to https://heimdall.mydomain.com or similar.

Now here comes the strange part. If I hit heimdall.mycomain.com in Chrome on my phone it loads perfectly. Same with my other apps. I have no idea what Firefox mobile is doing and searching around hasn't turned up anything recent or useful.

Is there something wrong with how Firefox on Android handles the headers? Why does Chrome not have this problem? I'm running Android 15 on a Pixel 7 so it's not a terribly old phone. This is causing a bunch of apps to fail as well (Sympfonium / Tempo for Navidrome). I am fairly certain everything is set up correctly because I can access my applications just fine from an iPhone / iPad using various apps as well.

2

What does "Address not found" mean? Does Firefox try to access the network, resolve domain to IP, try to connect to server? Maybe the FQDN DNS resolve is still cached in Firefox? Did you change it?

Enable and check Traefik debug log (doc) and Traefik access log in JSON format (doc).

3

That's what Firefox says when trying to connect to https://navidrome.myserver.com
Here's what it looks like in Firefox Mobile:

And here it is working in Chrome:

I've cleared every cache from Firefox that I can find, uninstalled it, reinstalled it and have even tried the Beta of Firefox but nothing works. Yet Chrome has no problem.

I'll try and check the logs of Traefik, I was having trouble turning them on in v3

4

Oh and if it helps here are the labels I have setup in my Navidrome docker compose file:

labels:
  - "diun.enable=true"
  - "traefik.enable=true"
  - "traefik.http.routers.navidrome.rule=Host(`navidrome.myserver.com`)"
  - "traefik.http.routers.navidrome.entrypoints=https"
  - "traefik.http.routers.navidrome.tls=true"
  - "traefik.http.routers.navidrome.tls.certresolver=cloudflare"
  - "traefik.http.services.navidrome.loadbalancer.server.port=4533"
5

Any PiHole or similar used?

6

Yep, I've got pihole running on a separate vm (192.168.1.14) whereas the docker host runs on 192.168.1.3.

navidrome.mydomain.com is populated in Pihole's List of local CNAME records along with all my other apps, they all resolve just fine.

I've got the logs working and Traefik is not seeing a single thing coming from Firefox Mobile or one of the Android apps. It sees Chrome requests just fine however:

-Content-Type-Options":"nosniff","downstream_X-Frame-Options":"DENY","entryPointName":"https","level":"info","msg":"","request_Accept":"/","request_Accept-Encoding":"identity;q=1, *;q=0","request_Accept-Language":"en-US,en;q=0.9","request_Cookie":"nd-player-6a61736f6e=Y1z2NUNTH316aoaQbMD0YZ; X-ND-Client-Unique-Id=0e95da95-7f17-4787-b685-f99f33758d84","request_If-Range":"Mon, 17 Mar 2025 12:56:14 GMT","request_Priority":"i","request_Range":"bytes=3538944-15876879","request_Referer":"https://navidrome.REDACTED.com/app/","request_Sec-Ch-Ua":"\"Chromium\";v=\"134\", "Not:A-Brand";v="24", "Google Chrome";v="134"","request_Sec-Ch-Ua-Mobile":"?1","request_Sec-Ch-Ua-Platform":""Android"","request_Sec-Fetch-Dest":"audio","request_Sec-Fetch-Mode":"no-cors","request_Sec-Fetch-Site":"same-origin","request_User-Agent":"REDACTED","request_X-Forwarded-Host":"navidrome.REDACTED.com","request_X-Forwarded-Port":"443","request_X-Forwarded-Proto":"https","request_X-Forwarded-Server":"8d4a360e4bf3","request_X-Real-Ip":"192.168.1.26","time":"2025-03-19T16:27:26+01:00"}

192.168.1.26 is the static IP I gave my phone while troubleshooting this, it's gotta be something to do with how Android / Firefox is handling things, the fact that nothing is popping up in the logs as soon as I try to go to the hostname feels like something is firewalling traffic from my phone itself.