Tried everything. Android app still says Plex server is "offline."

Ok, I’ve been browsing the forums, Reddit and Google for a solution for this. I’ve tried every configuration, temporary solution and setting described everywhere, and still my server appears offline. HELLO PLEX STAFF MEMBERS: we need a solution for this. I have seen posts here in this forum from as far back as 2019!
My environment is Docker (EDIT: on Linux) and everything is up to date, EDIT: including my phone’s app.
EDIT: My firewall is disabled and I only use the app at home.