I tried Upgrading to 20.11.05.010 and database schema fails to upgrade with : Upgrade to 22.11.05.010 [12:59:19]: Bug 33489 - Add indices to default patron search fields ERROR - {UNKNOWN}: DBI Exception: DBD::mysql::db do failed: BLOB/TEXT column 'middle_name' used in key specification without a key length at /usr/share/koha/lib/C4/Installer.pm line 743
Hi, this has been fixed by new Debian packages a little time ago. Please try to update again.