Same issue here. I didn’t notice the federation debug thing until I read it in this post but it won’t stay enabled for me either. I’m running v0.18.0 for both backend and frontend.
I tried to federate my instance with your instance. I can discover it via search and see some basic info about it (e.g. I see your account is a moderator) but when I try to subscribe it stays stuck on “Subscribe Pending” and my instance is not listed on the instances synced with your instance at https://etaorion.org/instances.
I encountered some errors like this when trying to federate with instances earlier today, though I am not seeing them now. Do you by any chance have anything similar in your logs?
lemmy-lemmy-1 | 2023-07-03T16:39:19.273338Z WARN activitypub_federation::activity_queue: Queueing activity <omitted> to https://lemmy.world/inbox for retry after failure with status 502 Bad Gateway: <html>
lemmy-lemmy-1 | <head><title>502 Bad Gateway</title></head>
lemmy-lemmy-1 | <body>
lemmy-lemmy-1 | <center><h1>502 Bad Gateway</h1></center>
lemmy-lemmy-1 | <hr><center>nginx/1.18.0 (Ubuntu)</center>
lemmy-lemmy-1 | </body>
lemmy-lemmy-1 | </html>
lemmy-lemmy-1 | . Sleeping for 60s and trying again
Also, one thing I notice about your instance on my own instances list is that the “Software” and “Version” columns are blank, unlike most other instances on my list which display “lemmy” in the software column and the relevant version in the “Version” column. Not sure if that’s significant.