Hi,

What about other open tabs? Don't you have "Browsing history" enabled in "Delete browsing data on quit"?

Hi! I found out that this could be a bug right now. The "Delete browsing data after exit" option is checked, under this setting only the "delete history" and "delete cache" options are checked. The "Opened tabs" are not checked, but even when I exit firefox, it closes all of my opened tabs. I used these setting from 5 years ago without any problems.

Yep, unfortunately, that's a bug (in Nightly and Beta). See https://bugzilla.mozilla.org/show_bug.cgi?id=2033285

Ridiculous question: Do you think I could get back my closed tabs somehow? Maybe they can send me a log?

Hate to say this, but I'm not sure that's possible... First, Mozilla definitely doesn't store any of your data unless you use Sync (and in that case, your old data have most likely been already overridden... but you can give it a try if syncing of open tabs was enabled). Regarding restoring tabs from some file on your device... even if something like that is theoretically possible, I have no idea of how this process might look like. You can try to post any reply here and see if other contributors have better suggestions