Network Configuration for VM (What am I missing?)

Hello everyone. Been trying to get away from TrueCharts, so I stood up my own VM (Ubuntu 24.04), installed Docker Engine/Compose (I’m new to all of this), and so far managed to get PiHole, Nginx Proxy Manager, and Mealie up-and-running.

Sort of. All of these services are accessible via IP/Port, but I’m struggling with the proxy part of things. I DO have Nginx properly working for domains to other devices on my network (UniFi, Modem), but it seems everything related to this same TrueNAS server (Home Assistant running on a different VM, Mealie running in a different Docker container) just times out with a 502 error when trying to access them using the domain name.

I’m fairly confident at this point that all of my configs are correct in PiHole, Nginx, etc. and I’m starting to think this is some sort of a configuration error on my part with the VM itself, which is preventing it from talking to other things on the same machine? I vaguely remember fighting with this issue for several days a long time ago when I first spun up my Home Assistant VM, but I am struggling now to pinpoint the issue.

Any help would be appreciated, and please treat me as a novice, because I very much am!

Do you mean you’re unable to talk back to TrueNAS / Other apps from the VM you’re running Nginx proxy manager in?
Do you have a bridge interface configured and attached to your VMs?

Well… I’m not sure. It seems I both can and can’t, though I realize that’s just my not understanding what is happening.

Take, for example, Mealie, which is running in another Docker container alongside Nginx. I can type in that IP address in a web browser in Ubuntu and it works. However, if I use the domain I’ve configured in Nginx instead, I get a 502 error.

So… actually maybe my issue isn’t with the VM configuration, as those are both adjacent docker containers next to each other inside of the VM, and I’d imagine should be able to talk to each other regardless, right?

I have the same setup as you. If you like some help reach out to me. I can walk you through the setup and show you how I did mine and got it all working. Just shoot me a message on discord @ aion_00