NVIDIAs latest beta driver 555.52.04 is OK on a 2023 HP Envy 17 laptop, but on my main system (HP 840 – kernel 6.9.3 – GTX 1070 Ti) it kills the HDMI signal.   The console (remote login..) shows:

[81362.885957] [drm:drm_new_set_master [drm]] *ERROR* [nvidia-drm] [GPU ID 0x00000800] Failed to grab modeset ownership
[81362.896271] [drm:drm_new_set_master [drm]] *ERROR* [nvidia-drm] [GPU ID 0x00000800] Failed to grab modeset ownership
……………..
[81363.134842] [drm:drm_new_set_master [drm]] *ERROR* [nvidia-drm] [GPU ID 0x00000800] Failed to grab modeset ownership
[81363.145361] [drm:drm_new_set_master [drm]] *ERROR* [nvidia-drm] [GPU ID 0x00000800] Failed to grab modeset ownership

According to comments on the NVIDIA Forum – these errors are supposed to be harmless (?)

The solution is to revert to driver 550.90.07, for the time being..

Robert Gadsdon.   June 10th 2024.