Hello! I have a similar problem – a black screen and a mouse cursor. I think GDM3 does not start. The problem was noticed around Jul 30. The client and the Server are both on Ubuntu 22.04. Client on the Mesa Radeon by Ubuntu community driver, and server on proprietary Nvidia v.470 driver. NoMachine v.7.10.1 deb64
Until Jul 30, the problem was not observed. It worked all before. NoMachine settings have not changed. Only updated core and video drivers.