Ubuntumate 20.04 not booting after Update

[ironfoot]

We still don't know if mentioned bug is what affects you, because we haven't seen any error messages. If you press Esc after grub menu, in your HP logo boot stage, does it show any error?

Anyway, you need to boot from livecd or liveusb.
If you want to test the mentioned workaround, you'll have to (if I understood it correctly) chroot into your broken installation and manually update your volume group metadata using vgck --updatemetadata VGubuntu-mate command. I assume VGubuntu-mate is your volume group name based on your previous posts.
If you don't want all this, the most straightforward solution will be to boot from livecd or liveusb, mount your logical volume, copy all sensitive data from previous installation, then repartition your disk to a configuration that is more familiar to you (since you have to support this system). Then perform clean install.

[monamtb]

Hello Ironfoot,

Thanks, I don't een know how to CHROOT into my broken installation.
SInce i made a Backup with Deja Dup I performed a clean install with a separate /home partition now - the system now boots up fine, I am playing in the backup at this moment and then will figure out which programs need a fresh install.

By the way - using GParted I first needed to "unlock" the LVM partitions created - I couldn't delete them at first and had to find out first how to remove the security key in GParted.

Thank you all who devoted their time to solve this issue.

At this point I consider this issue solved by performing a new clean install.

[ironfoot]

You are welcome @monamtb. Sorry, I am not very familiar with LVM setups. Maybe more elegant solutions to your problem exist as well.