Yeah, I feel like we’re missing some info here.
I have to admit that I have no experience with yuno. Always seemed interesting, but not like something that fits into my work flow.
If they’re self-hosting at home (which I’m also doing for some services), I’d presume they’re probably running their stuff on a single machine, so I’m not sure where their router would come Into it. The data the cloudflare tunnel process receives should look the same to the router no matter the port it is ultimately sent to, and when it is sent to an address internal to the machine, shouldn’t pass through the router again.
I’m also in Germany. Most banks offer either a credit or debit Visa or MasterCard, with the debit version usually being accepted like a credit card would be, excluding some edge cases.
Even Sparkassen seem to slowly be transitioning to that option, though it took them 10 years longer than everyone else. So, unless you don’t want to use a Visa or MasterCard for philosophical reasons (which I could understand, their stranglehold on the market is very annoying), your bank probably offers something that would be accepted there.