You can enable saving the tabs when closing Firefox.
It is on and has been for years but I still lose all my tabs regularly.
Is it because of Sync? Container Tabs? I don't know
If I'm not too mad next time, I will try to find out why I lose them but my instinct is to reopen right away the tabs that I need the most.
When I read this kind of stories about game dev where unit tests are very optional, I don’t really regret not working in this industry, especially now with all the layoffs.