Hey all.
I have a Lenovo 430 and a T440s.
Both gave simular problems.
First I tried upgrade following the instructions, the problem was it failed to show a "normal" window after upgrading - giving total useless GUI.
Then I tried to install a fresh 21 Cinnamon on both laptops.
Both showed grub in upper left corner when booting - and gave me no options to continue.
For testing I tried install 21 XFCE - same result - grub in the upper left corner.
Your suggestions - please
Regards
John