[ISSUE] gdm does not launch after enabling nvidia DRM (nvidia optimus)

[ISSUE] gdm does not launch after enabling nvidia DRM (nvidia optimus)

[zxvr0]

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New issue by zxvr0 on void-packages repository

https://github.com/void-linux/void-packages/issues/45406

Description:
### Is this a new report?

Yes

### System Info

Void 6.3.13_1 x86_64 GenuineIntel uptodate rrrmmnFFFFFFFF

### Package(s) Affected

gdm-44.1_2, nvidia-535.86.05_1

### Does a report exist for this bug with the project's home (upstream) and/or another distro?

_No response_

### Expected behaviour

Setting the `nvidia_drm.modeset=1` kernel parameter (or `options nvidia-drm modeset=1 ` in /etc/modprobe.d) enables nvidida Direct Rendering Manager KMS and gdm works like usual.

### Actual behaviour

Setting the kernel parameter and starting gdm freezes the entire system, i.e. even switching to an another tty is impossible.

### Steps to reproduce

1. install the nvidia proprietary driver and gnome; enable dbus
2. set the `nvidia_drm.modeset=1`  kernel parameter (through grub in my case)
3. start the gdm service

Re: gdm does not launch after enabling nvidia DRM (nvidia optimus)

[paper42]

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New comment by paper42 on void-packages repository

https://github.com/void-linux/void-packages/issues/45406#issuecomment-1665522664

Comment:
could you try forcing the xorg backend in gdm's settings? If you can't switch ttys, it's probably using Wayland.

Re: gdm does not launch after enabling nvidia DRM (nvidia optimus)

[zxvr0]

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New comment by zxvr0 on void-packages repository

https://github.com/void-linux/void-packages/issues/45406#issuecomment-1665671477

Comment:
the issue persists trying both `WaylandEnable=false` and `true`.  other things I've tried:

- enabling/disabling hybrid mode (have the laptop use only nvidia)
- enabling early KMS 

i think the following message from the kernel log may be relevant:
`gdm: Gdm: GdmDisplay: Session never registered, failing`
in addition, i've tried enabling DRM on a fresh arch install to check if this is a hardware issue, and it seemed to work fine.