Yes me too.
They broke my phone. FP3 with Android10 = randomreboots.
See this: Android 10 with bugs - e.g. reboots (build ....0045)
And yes, I have contacted support too.
They should really not wrongly announce a beta version as an essential upgrade, that is very bad style IMHO.
Any FP veterans here? --> how many hours days weeks months years does it usually take until new versions are released?
Phone is declared BROKEN until new build is released.