Cannot stay logged in on desktop

Since a few weeks ago, Lemmy.world will always log me out when I leave it, and I cannot find a "stay logged-in" tick-box anywhere in the settings. Is this a bug or a feature or perhaps a "me-problem"?

Happens with Firefox and Vivaldi on Linux, if that matters. Emptying cache/cookies did not help. Mobile app is fine.

Thanks for any hint!

ETA, thanks to @Rooki@lemmy.world, there is a temporary workaround to this:

I could set the lemmy.world cookie to “lax” using a cookie manager extension. Now it seems to work, both with F5 and when I leave Firefox.