I have similar problems. When I go to jitsi, for ex.
https://meet.jit.si/toto, firefox is unresponsive: it does not finish
loading the tab (the blue point in the tab moves left-right), and
clicking anywhere in firefox window (menu, tabs, page content) does not
change anything. I need to kill it with ctrl-c (in linux). Nothing is
exchanged on the network; CPU is small, cf. 'top' tool:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+
COMMAND
15790 ededu 20 0 3376132 402248 170036 S 13.3 2.5 0:19.66
GeckoMain
However, it is the first time I see GeckoMain shown in the first lines
of 'top' (13.3% in the example above).
Downgrading from 93.0-1+b1 to 93.0-1 fixes the problem.