[Koha] Upgrade to 21.11 Fails

[Asst. Sec. Bruce A. Metcalf]

Hi gang

Back again after a forced suspension of work.

I am trying to upgrade from Koha 21.05 on Debian 9 to 21.11 
(OldOldStable) on Debian 10.

The upgrade appears to go through, but both public and staff interface 
display [Internal Server Error].

System was working fine on 21.05/9, and all but Koha work under Debian 10.

All suggestions will be appreciated.

Cheers,
/ Bruce /
Bruce A. Metcalf, Librarian
Augustan Library