Official debian updates

Hello everyone,
I have just booted up my Rock5b for the first time using the official debain fro an eMMC and am pleasantly surprised. It is very responsive even while playing 1080p videos in the background while just consuming about 5W of power.
However, I am very unsure about updating my board and have received some errors while trying to do so: First and foremost I am a little irritated with the debian bullseye official sources (debian.org bullseye) being in the sources.list. Is this by purpose? I thought the sources should be the radaxa ones. Secondly, when I try to update with these sources using apt update, it gives me an error about the radaxa.com bullseye sources not being verified because it is missing the public key. However, this source is not present in the sources.list. So what sources should I use and how is the distro intended to be updated? Can I just do it via apt update and then apt upgrade?

The official Wiki has some very strange recommendations, but as far as I think it is not up to date as the sources.list does not seem to be the one I got with the image I downloaded 1h ago.

Thanks for any clarification you can provide.
If anyone who is developing the distro is reading this: I also had performance issues while viewing youtube videos in fullscreen. They played fine in the normal windowed player. This might be because I am using an ultrawide monitor and a resolution of 3840x2160p. Still impressed by this little thing just being able to drive this huge screen.