Well, today Firefox froze two times in a row, after a week without any troubles.I'd mark it solved, as we've at least found the problem and you have a workaround. You can also test it now and then to see if the problem has been fixed. You could try reporting a bug at Google, but good luck with that... It might be easier to try reporting it as a bug to one of the derivatives, like Opera. They're pretty receptive.
This is why I am not sure booting from text-mode is a good idea. It might look like there is no problem, but after a week it will randomly give some error and freeze. Or after a month, who knows.
I wonder if these freezes are caused by Windows, because I had Linux installed previously on this same laptop and there was something similar happening. It would freeze randomly and I would have to restart, but it was also somehow changing the bios settings - turning on safe boot and switching from AHCI to RST optane, which is not happening here.
I'm not sure whether these problems are related, but maybe?