Today I tried to restore a full backup of an old DB to a new database with

what resulted in
RMAN-06026: some targets not found - aborting restore
RMAN-06023: no backup or copy of datafile 6 found to restore
After looking for the solution for hours I found out that there is a 5-year!!! old bug open that makes it impossible for RMAN to restore a backuppiece if it's read-only.
The BUG# is "5412531 - RMAN FAILS RESTORING READONLY BACKUPS: ORA-19870 ORA-19587 ORA-27091 ORA-27067"