Boot fails after upgrade, failed to start "Postfix Mail Transport Agent"

Today I upgraded from Leap 15.2 to 15.3. Everything seemed to be going well, but when I attempted to boot, I got an error that says:

Failed to start Postfix Mail Transport Agent.

I found some posts that suggest editing a file in the computer or disabling IvP6 protocol (if I remember correctly). But I’m not sure how to do that from Grub.

Can anyone guide me?

Full disclosure, I did encounter a conflict regarding a virtualbox package. After reading about solutions online, it was suggested it could be ignored and fixed later in Yast. So I chose to ignore it.

It looks like I cannot do much from GRUB GNU. I do have a bootable USB, that I can use for rescue mode.

Any other ideas on how to resuscitate this machine?

This is solved.

I just booted from USB and choose upgrade and was able to preform a successful install