Gnome Screen Sharing (VNC) does not share all monitors
Using Fedora 35 beta with latest updates, screen sharing only sends the primary monitor. I have used vino on Ubuntu before, which was admittedly slow and buggy, I was able to see all the monitors of a desktop. I tested with Remmina and Gnome Connections. If usability is a concern, perhaps Connections can offer a switch displays options to lets you select the monitor you wish to view.