happens to me too. but i would bet money it's because of memory corruption in both of our cases.
i have the exact same setup on ECC ram and zero crashes. on non ECC (cheap, garbage, that everyone accepted as the default) ram, one crash every couple weeks.
so unless you can prove software on the same cpu is non deterministic, it is ram corruption.
I've never used Ubuntu, but on Fedora and openSUSE Tumbleweed, I've never run into this issue (and I've had like 50+ tabs open for weeks since i don't really reboot my work laptop unless I have to)
I'm not sure how this contributes to the thread. This isn't a technical support forum, so it might not be the best place to discuss specific browser issues.
I've been using Firefox on Ubuntu since 18.04 was first released (about 6 years ago), and while I've encountered some issues, I haven't experienced the problem you're describing.
Of course, browser performance can be affected by many factors in your system. If you're seeking help, you might have better luck in a dedicated support forum or the official Firefox support channels.
Does it freeze completely (forcing you to resort to kill -9) or is it just slow?
In any case, I've been been a Ubuntu user since ~2010 (and a Firefox user since its inception). I remember there being a time when Firefox was slower than Chrome and freezing occasionally but that was a looong time ago and I haven't had any issues with performance or freezes/crashes ever since.
