Ah, darn. Unfortunately I have no additional help to offer since that particular issue was fixed for me after changing those options in Flatseal.
I’d try running Firefox from the terminal to see what error message you’re receiving when the crashes occur; the unique error message was what led me to this workaround when I was originally troubleshooting.
That sucks to hear.
Glad the threat actors didn’t get the payout they were hoping for.