I've done everything per the instructions on this page:
https://www.teamviewer.com/en/global/support/knowledge-base/teamviewer-remote/remote-control/add-a-virtual-monitor-to-your-remote-device/
Usually I connect through LAN using the local network IP address of the remote PC, but in order to try to get this option available I switched to connecting through easy access from the managed devices section on the client.
- Both devices are running Windows 11.
- Both devices are managed and have easy access enabled.
- Both devices have mid-high end GPUs with up-to-date drivers and have physical monitors attached to them.
- Both devices are running TeamViewer (full-client)
===== Client Info =====
UI version: 15.68.5
Commit hash: 4103faf4f2
===== Server Info =====
Host version: 15.68.5
Commit hash: e05bb777c5e
Build date: 2025-07-24T15:24:43Z