The server will be down from 18:00 UTC for possibly one hour (not sure how long exactly) to replace the current docker + compose setup with an ansible setup. This is to hopefully fix any current federation problems, and if not, then to at least eliminate any issues software wise.
On a related note - If you're a technowizard, especially when it comes to ActivityPub and Lemmy BE, please message me (either here, over email, Discord (nullishcat), Matrix (nullishcat:matrix.org), or Divolt.) I still do not know the root cause of this problem and have nearly exhausted all potential fixes (the remaining ones being this setup change and switching providers.)
Technical details can be found here: https://github.com/LemmyNet/lemmy/issues/3862#issuecomment-1711051012
EDIT: We're back up, very sorry for the long wait. (Ansible's setup guide is very poor and didn't make it clear that it needs to be run on a local PC running Linux/Mac and to copy the volumes to /srv/lemmy/volumes.) Federation tests will start shortly.