Found a bug in #snac where it would give a 404 error if I entered my base URL instead of showing the greeting.html page. Started thinking I'd messed up my nginx reverse proxy config somehow but couldn't see anything wrong. So decided to bypass the reverse proxy and use curl on my snac instance to prove that it was snac that was the issue. Anyway reported and a fix has been found by another snac user which I tested and @grunfink@comam.es pushed an update.
Proof that reporting issues and testing with the devs does indeed help.
The now closed issue is below.

https://codeberg.org/grunfink/snac2/issues/282