Hello Hrfuchs49,
I'm not working with Mac OS Big Sur yet and I'm not burning Blue Ray's at the moment. According to Asus, however, the drive should be supported from OS X 10.6 and higher. Blue Ray formats are also supported. There are write-once and rewritable formats. The capacity is also important. There is the single layer (SL) with 25GB and the dual layer (DL) with 50GB. You can find out exactly which formats they are in the link I've attached below. What you still need is a burning software. Either a freeware or a paid one. Mac OS X cannot burn a Blue Ray by itself. However, programmes from Apple itself, such as Finalcut or Compressor, can burn Blue Ray.

Link Asus:
https://www.asus.com/ch-de...

Link free burning software:
https://burn-osx.sourceforge.io/Pages...

Or the paid software, e.g. Toast from Roxio or Nero.

Greetings from Carlo