With parallels 17.1.1 Ubuntu 20.04 is hanging on boot with kernels 5.13.0-35 and 5.13.0-37. 5.13.0-32 works.
A number of folks, including me, are getting this issue. There are already a couple of threads opened in the last week about this. Clearly something has recently broken either in the linux kernel (unlikely) or in Parallels (more likely) - we're hoping that as it was quickly introduced, it can be just as quickly addressed (but then, I'm an optimist ).
Further to the above, the problem doesn't seem to be specific to a single kernel version, but to a particular configuration of kernel. I have a VM which installed as Ubuntu 18.04 (worked fine - kernel version 4.15) then failed to boot when upgraded to 20.04 (kernel 5.4) but booted OK when previous kernel selected in grub.
Nearly the same issue here: hanging on boot with kernel 5.13.0-35 fine on boot with kernel 5.13.0-28 (Parallels 17.1.1, Ubuntu 20.04)
Yes that commit revealed the bug in parallels I posted the reason in https://forum.parallels.com/threads/official-ubuntu-20-04-live-server-does-not-boot.356891/ However I've been unable to get past first line support.