Hello fellow selfhosters! I changed my server OS from fedora server to alma linux as I wanted a more stable base with less frequent updates for my docker containers, so I backed everything up and installed almalinux. It all went smoothly, and now all the containers seem to work as before except for nginx proxy manager: on fedora, I set all the proxy hosts like this (using jellyfin for instance): jellyfin.mydomain.duckdns.org > http://myserverhostname:8096 now, for some strange reasons, it does not work anymore, and I get a bad gateway error. I tried with and without SSL (that I had from the previous installation, do I need to regenerate them? but without it should work anyway...), pointing to localhost:8096, to myserverhostname:8096, to jellyfin:8096, but nothing. The only way I could make it work was with the resolved IP address of my server:

# host myserverhostname
myserverhostname.station has address 192.168.1.13

pointing nginx to 192.168.1.13:8096 correctly shows the website. why does this happens? am I doing something wrong?

EDIT: the only one that's working with localhost is nginx itself (http://localhost:81)

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SOLUTION: instead of myserverhostname, in nginx proxy host configuration (in the gui) I had to set myserverhostname.station to get it working. I don't know why, in the previous installation only the hostname was enough...