@ogrfnkl Your problem seems the most similar to mine. It's been a few days since my Opera started to crash randomly. After one of those crashes all my opened tabs were gone. To cut the long story short: I've tried various things, and finally I uninstalled the browser completely, removing all of the personal data (I made a copy of it). Then I downloaded Opera Beta (instead of Opera Stable which I used previously). The only data I copied from the old installation was bookmarks, favicons, and history, which I think cannot be corrupted and do any harm. I installed only a few essential extensions configuring them from fresh. So it was a completely new installation.
And yet it still crashes once every few hours.
The system is Windows 11 with all the updates. Opera is updated, too.
Any ideas?