Black screen after login

Distribution

Linux Mint 22.1

Package version

Cinnamon 6.4.8

Graphics hardware in use

Intel® Graphics (MTL)

Frequency

Always

Bug description

Occurred in the past only occasionally, now persistently. In the past, reboot helped, but not anymore.

Normal startup and login box appears, but after login the screen remains black, mouse is visible and moves. When I switch an external monitor on or off, the screen shortly goes black, mouse appears again, so second screen is detected. When I press Control - Alt - Backspace, I see for a fraction of a second the background, symbols and things, so the screen has been rendered but is not shown. I also waited for about 3 minutes (see bug #9898, which is not really the same issue, so I started a new thread). I tried different things to get around the problem.
Using the previous kernel at startup: Does not fix the problem. Removed some extensions (after using another display manager). Using Wayland, results in crashes. The version and Hardware is shown with "uname -r" as:

• Linux HP440 6.8.0-71-generic #71-Ubuntu SMP PREEMPT_DYNAMIC Tue Jul 22 16:52:38 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

For the sake of completeness:

• Intel Core Ultra 5 125U x 14
• Gnome version 46

I can open a terminal session outside gdm3 and login or doing ssh from another machine, no problem. It is just that the display manager seems to put a black curtain between desktop and mouse and does not accept input from keyboard or mouse buttons.

At login, I can choose from

• Cinnamon -> crashes (shows bad face on a monitor and says "something crashed"), so I never used it - this is not the issue described above
• Cinnamon on Wayland -> crashes (bad face) - but Wayland is experimental
• Cinnamon (software rendering) - worked in the past, now making problems - the bug report refers to this display manager
• Ubuntu on Wayland -> Starts up but messes up things, for example problems loading iBus, fixing keyboard to US layout - I don't like it
• Ubuntu on Xorg - works fine, so I have a workaround to the problem, had only to re-install a few little extras to get the same desktop
  I still want to know what went wrong.
  Any feedback is appreciated

Steps to reproduce

Reboot and at login on display manager choose "Cinnamon (software rendering)"

Expected behavior

Show desktop and react to keyboard and mouse input (mouse movements are shown, though)

Additional information

No response

Start by reproducing the issue after rebooting and selecting Cinnamon (software rendering) at the display manager, using the reported Linux Mint and Intel hardware context. Compare the working Ubuntu on Xorg session and the black-screen session, then inspect available Cinnamon and display-manager diagnostics. Done means the Cinnamon desktop appears and accepts keyboard and mouse input after login.