SEPA discrimination is illegal but a fact. Many sellers don't even let you enter an account number that doesn't start with DE. At the latest the Schufa check will fail.

then just buy with one of the providers which don't have the issue... not all need schufa checks

Easier for those who sell themselves to Google or pay the Apple premium. For people who believe in freedom it means a chipcard. Which can be a real challenge because then the number of sellers gets very small and they might be very far from where you'd like to buy it.