update 26.7.1 to 26.7.2 fails, no boot on legacy boot system after reboot

[knowHoff]

Good evening,

after doing the upgrade today from
26.7.1 to 26.7.2,
my system fails while trying to boot.
The only output I see is the one shown here

You cannot view this attachment.

I am able to access a boot prompt.
The only answer I get after typing "boot" is from gptboot, which is not applicable on a CSM / legacy boot system.

You cannot view this attachment.

Is there any possibility to recover the installation
or do I have to clean install?

Cheers