I just installed the Logi Options+ App on MacOS Big Sur and already previous was running Logi Options App. The new app is sitting at the Good Afternoon screen waiting for my MX Master 3 mouse (which does seem to work still. It was Bluetooth connected). I had to switch to position 2 on the mouse and plugin the Logi Unity USB. You should update your instructions. I normally do not use the Unity dongle because I only have USB-C ports on my Macbook Pro.