I can confirm the copy / paste problem with TightVNC 2.8.63 Client on Windows 11 21H2 22000.348 with several workstations running the same TightVNC server version. Sometimes copy / paste works, sometimes not. Could not find out any rules when it works and when not :-(
Corrected: Intel HD Graphics 4600 - Driver 20.19.15.5144 and with Driver 20.19.15.5126 (original Windows 11 driver)
Black or frozen Screen on Windows 11 with Energy Saving Mode on Display Port