Your 2nd link refers to Cryptomator Version 1.4.x and is outdated.
As far as I know Big Sur is supported. But there are problem reported with 3rd party app FUSE if not updated to the very latest developer version. I’m assuming there will be a new release of FUSE for Big Sure in the near future.
So if you are using FUSE as vault file system, please read here: Big Sur - Cannot open vault anymore
(Disclaimer: I do not use macOS.)