Ubuntu. Old mouse was wired while new mouse is Bluetooth. Might be related to that.
Discussion
Remmina or some other remote access installed?
No 2.4GHz dongle option? Usually most BT mice come with both...
Probably wireless interference of some kind. Happens frequently with certain models that don’t do a good job encrypting / authenticating traffic between the mouse and receiver. Does it go away if you unplug the mouse?