x11vncd + vbox-standalone

To run x11vncd to manage vbox-standalone, copy x11vncd.service to /etc/systemd/system and change User to vbox. Otherwise, we will see an error:

Hello,
Since the latest xorg update. x11vnc doesn’t work on GDM. I get the following error message:
Dec 11 16:09:03 PC x11vnc[1032]: caught X11 error:
Dec 11 16:09:03 PC x11vnc[1032]: 11/12/2020 16:09:03 deleted 60 tile_row polling images.
Dec 11 16:09:03 PC x11vnc[1032]: X Error of failed request: BadAccess (attempt to access private resource denied)
Dec 11 16:09:03 PC x11vnc[1032]: Major opcode of failed request: 130 (MIT-SHM)
Dec 11 16:09:03 PC x11vnc[1032]: Minor opcode of failed request: 1 (X_ShmAttach)
Dec 11 16:09:03 PC x11vnc[1032]: Serial number of failed request: 57
Dec 11 16:09:03 PC x11vnc[1032]: Current serial number in output stream: 119