I used testing for ages, it is really stable. Only the phase after a feature freeze for the release of a stable version can be a bit shaky. For some weeks I just change my repos to the stable version.

That is standard in all of Debian, just get it as a flatpack.

I can’t go past the cookie banner with Firefox. Chrome optimised?

But the project can be found at https://openrgb.org/

Same story, same tips, but I started with SuSE Linux 4.3 in 1996. Just try stuff, read the error messages, read docs and ask. A lot of peaople who know stuff are happy to help out of altruism or the chance to show off. ;-)