So I have been in the process of switching computers. On the old one (a much older Macbook Pro that had Catalina I was still using Cura 4.7 and everything was fine (sure, things got weird sometimes but the same as any other program really). I'm moving to a newer Macbook Pro (still Intel-based) with Big Sur and I installed Cura (4.9.1) today and I can't select anything. Found this forum post, so at least I know it's not just me, but there doesn't seem to be any solution that I see.
I had seen some others talk about adding 'full disk access' rights to Cura for some slightly different mouse issues in other threads, but I tried that and it didn't make any difference. For the moment I can probably live with it and just use my old computer if I need to manipulate objects separately (since all I can do is select all objects) but a fix would be good!