Right now it works with kernel 5.8 but in 5.11 (installed this morning along other upgrades) the wifi adapter doesn't get detected at all and apparently there are no fixes until the drivers gets patched (unless i'm mistaken). Do someone know if/when bcmwl-kernel-source will get patched?
edit: current version of bcmwl-kernel-source is 6.30.223.271+bdcom-0ubuntu7
PS: To be honest each time there's a kernel upgrade this adapter stops working... it's quite frustrating
So i solved the issue by downloading a binary (deb) from here: https://launchpad.net/ubuntu/+source/bcmwl/6.30.223.271+bdcom-0ubuntu7~20.04.3
I uninstalled what i had, and installed bcmwl-kernel-source_6.30.223.271+bdcom-0ubuntu7_20.04.3_amd64.deb which was backported from Irsute Hippo which installs kernel 5.11 by default.
Before i had solved a similar issue from 5.4 to 5.8 by installing this binary bcmwl-kernel-source_6.30.223.271+bdcom-0ubuntu7_amd64.deb
Same version basically but fixed for 5.11. Probably that's why apt said i had the latest version installed (which was truish).
Hope this helps someone else.