I have a Dell Latitude 5491 running 19.10 which hangs at the initramfs subsequent to the capsule firmware update which was released on 26 Feb 2020.
If I boot from USB I can access the drive (encrypted) but the system will no longer boot either kernel 29 or 40, both hang at initramfs.
There is some mention during the update that grub will be changing to /dev/dm2 when it restarts. I cannot find reference to /dev/dm2 or dm1 for that matter anywhere.
If I do not apply the updates which have been made available since 19.10 was released the system will continue to run...
So I'm currently not updating. I'll likely wait until 20.04