So the keyboard worked for the AV wizard?
Meanwhile (after installing on a different computer), I found what might be the problem.
On the first system, I installed all the kubuntu upgrades, which were offered by auto-update.
AFTER that, I installed LMCE.
On the second system, I did not apply the updates... and the keyboard worked on the wizard.
So I tried that on the first system - and it worked also...