Yes pairing is still possible via Blueetoth or with the following Logitech Unifying receiver adapter. Logitech Unifying software must be installed for the mouse to pair with the receiver.
This is the original MX Master mouse (i.e. version 1) in a no frills cardboard box. I bought this some time ago versus the slightly more expensive version in a color box like what you would find on a store shelf. Master 3 is a newer version as you can see for example the shape in front of the buttons. The other technical differences between Master (1) and 3 I could not say.
Hello Picofon. The side buttons can be assigned to any function. I have this mouse, but I don't use these extra buttons out of habit. In theory, however, I find the ergonomics quite good. As with any new "control element", it is probably simply a matter of habit whether one can then work efficiently with it or not.
Hoi Mig,
Here you can find a replacement: Logitech Pico USB Unifying Receiver
Alternatively, you can connect the MX Master directly via Bluetooth to your device (as long as the device supports Bluetooth of course) and thus do not need an adapter.