It seems Logitech MX Master and MX Keys don't work correctly with Apple's new Universal Control feature (now available to try in beta). When devices are primarily connected to Mac with Logi Options (or Options+) installed, unable to scroll or use gestures on iPad.

I don't know if this is something Logitech need to work on or Apple but at the moment it means I can't use Universal Control.

Others online have reported this issue specifically with MX Master devices too, other 3rd party bluetooth / USB devices work fine