Have you tried staying logged in on a separate unmodified browser? Sometimes my extensions have weird side effects
This is not the issue; and this test was already performed well in advance of the posting of this post. I am aware of every plugin I use and have a general idea about how it interacts with my browsing...not to mention several other browsers I can spin up with varying levels and degrees of plugins and protections to troubleshoot the issue.
Currently I am on Firefox 129.0; and have tested the following and observed the same behaviors:
I don't think it's only your instance. I'm on lemmy.world and every time I open Lemmy in a new tab, it seems to fail to retrieve my login credentials and I have to log back in again.
I seem to be getting randomly 'logged out' across reloads of the main page or post loads arbitrarily, refreshing the page again instead then recognizes I'm still logged in.