Iunno if I will get a response here, but it's worth a shot.

https://github.com/starfive-tech/linux/issues/135

There is a forum on rvspace, so I will try this after a few days too. That said, I can at least narrow it down to my kernel being the issue, which makes finding the issue at least a little bit easier. And, i am off to order that UART cable now. xD Before I totally forget to do it...