DO Not use “Brush” as although it appears to work as it would before Big Sur, there is no way of turning off the brush due to there being no Selective tool. You can access the other plugins from the filter menu edit as neccesary and return to whichever software you are using. The only thing that doesn’t work is the Nik Selective tool in photoshop. There is a folder in Applications called Nik Collection, but it is empty. I have just done this for a friend and it works for her. This is where you need to do a bit of work, locate the plugins on your drive and copy them to the plugins folders of whatever version of Photoshop and Lightroom you are using. If double click on each one in turn you can install them on Big Sur. Next select “Resources”, and you will see all of the individual install packages. A finder window will open, chose “Contents”. Open the installer, and when it is at the first screen, where you have the two options of either install or uninstall, right click on Nik Collection.app and select “Show Package Contents”.

There is a workaround that takes a bit of work.

Nik collection 4 mac m1