Just picked up a Logitech MX Master 3 for $80 on sale. I like the placement of the thumb buttons better than the ones on the MX 2 (which is now replacing my minuscule M310 at work), and the resolution seems better.
Also, the Bluetooth function is smoother... don't know if the solution to the laggy BT connection I last encountered a couple months ago is on the Linux side or the Logitech one, but the MX3 does not seem to have any lag compared to the Unifying receiver now.