I'm still using v4.20-rc7, and I wanted to try some more kernel parameters to narrow down the problem. Since the last kernel messages I got using earlyprintk (https://gist.githubusercontent.com/bmaupin/b743bb3325e100341c62ee62e713d8a4/raw/7372dddb5704d3f15ff429807355d5d3686165d2/boot7.png) were related to the Spectre mitigations, I removed noapic and replaced it with spec_store_bypass_disable=off and it booted. Oddly enough then I removed spec_store_bypass_disable=off altogether and it booted without any special parameters.
So I don't fully understand what happened, but it seems like my system boots fine now without any special parameters. I'll remove v4.20-rc next and see if it still boots with the kernels from Bionic.
I'm still using v4.20-rc7, and I wanted to try some more kernel parameters to narrow down the problem. Since the last kernel messages I got using earlyprintk (https:/ /gist.githubuse rcontent. com/bmaupin/ b743bb3325e1003 41c62ee62e713d8 a4/raw/ 7372dddb5704d3f 15ff429807355d5 d3686165d2/ boot7.png) were related to the Spectre mitigations, I removed noapic and replaced it with spec_store_ bypass_ disable= off and it booted. Oddly enough then I removed spec_store_ bypass_ disable= off altogether and it booted without any special parameters.
So I don't fully understand what happened, but it seems like my system boots fine now without any special parameters. I'll remove v4.20-rc next and see if it still boots with the kernels from Bionic.