Just use Nginx... It isn't that difficult, after all.
Or try any one of the "simplified" other proxies out there. I never seen the need for NPM anyway, as it just obfuscate nginx configuration stuff from your eyes.
You can check my wiki at https://wiki.gardiol.org/doku.php?id=selfhost%3Anginx
I wrote for my own benefit, and for others who might be interested.
Yes it's docker... Immich is only deployed via docker.
Indeed its your docker mount points / volumes.