In late 2020 I read the following on their website:
We now offer printed QSL cards for reception reports arriving (via post only) via the address of the World Wide DX Club:
Shortwave Radio, P.O.Box 1214, D-61282 Bad Homburg, Germany.
QSL policy: At least 30min of programme details incl. comments to the programme. Minimum 3 Euro return postage cash or via PayPal.
I immediately wrote a "snail mail" report to the address above and included 3€ into my envelope.
Finally - after quite a while - I received an answer with my QSL.
It was worth the effort and money to have received another confirmation.

BTW: In earlier times, it was also quite common to include return postage in the form of US dollars or IRCs with the reception reports,
regardless of whether they were sent to legal or illegal radio stations.