I too have no idea what this is about. I never used tailscale, and I have no idea what immich is.

But perhaps your problem is that the app expects to be on the root? Perhaps that could be a problem. Can you instead do another level sub-domain level like immich.pcname,tail$$$$$.ts.net? Or does the app (immich) allow you to set URL root?

Anyway, seems that may indeed be the issue, and also that tailscale cannot do those sub-domains as I thought based on the discussion I found. It seems this is the same issue: github.com/immich-app/immich/discussions/1679

And someone probably has a solution: gist.github.com/…/4b2b22b2198636b0a91c7c142ec11b3…

Again, I have no idea what Immich even is in the first place, Tailscale, I just know it exists. Consider me about as useful as AI, I just did some googling, with only prior info being that I had to set base URL in both kiwix-serve and Navidrome for them to work properly under a directory or whatever the part after slash is called.