pg_upgrade fails with lc_ctype cluster values do not match
You'll need to re-initdb the new database with LC_CTYPE set to de_DE (i.e. use a non-Unicode encoding); check the old DB's encoding and use the same one when you initdb the new database.

Alternately, use pg_dump and pg_restore to do a dump and reload of the old DB's contents into the new DB. This requires that you have the old DB running.