Reverse Proxy: One vHost with locations for different docker apps - eviltoast

My idea was to create one vHost myserver.local and have custom locations pointing to different docker apps:

myserver.local directly points to the NPM admin GUI on port 81.

myserver.local/portainer should point to portainer:8000

I tried it with NPM but it doesn’t seem work: I get to the admin GUI but only get a 404 for /portainer… Googling the issue I mostly read about using sub domains instead of locations, but at the moment I am limited to one DNS entry for my home server.

Any suggestions?