Key Bindings, Razer Synapse and MacOS Big Sur

Today I had to finally update to MacOs Big Sur, and by doing so I lost the functionalities of Razer Synapse - since they aren’t updating it for Mac anymore, apparently.

Is there any way I can still bind keys to mouse buttons 4, 6, 9, and 10? When I click on them in the Key Binding menu in-game, nothing happens anymore.

I also installed SteerMouse, but it seems to do absolutely nothing for the in-game key binds.

Any advice is very welcome, even if it only says “buy a new mouse”, and in that case I am happy to hear which one!