Edit :
On a “old” phone for witch no new update / upgrade will be ever released by Samsung,
Exact CSC No realy matter for using custom OSes, as we wipe /system and /data, the carriers addson apps will be erased
Important is the used CSC contains the right cellular bands used by the carrier in the country.
IN YOUR CASE, you could use ”DBT" witch is Deutsch free of carrier and all Deutsch carrier capable