I had the same problem, I usually buy AMD processors, but I read
about
the problem, I bought an Intel box. Still, the whole boot process
seemed to take place up, but ended in an infinite loop waiting for
startup process to end.
I ran into that also with F30, but it's not the same problem I'm reporting. That
problem was apparently RDRAND related, and is fixed in the version of systemd in F31. If I
install F31RC1.9 on the Ryzen 7 3800X _without_ filesystem encryption, it installs and
boots just fine.