Hi,

Thank you for the package in -proposed.

I just tested Ubuntu 22.04 and I can confirm it fixes the issue.

First, used 22.04 with the current mutter version available in jammy-updates:

user0@U-2RVWD6LKXR3GE:~$ sudo apt-cache policy mutter-common libmutter-10-0 gir1.2-mutter-10
mutter-common:
  Installed: 42.9-0ubuntu1
  Candidate: 42.9-0ubuntu1
  Version table:
 *** 42.9-0ubuntu1 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     42.0-3ubuntu2 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
libmutter-10-0:
  Installed: 42.9-0ubuntu1
  Candidate: 42.9-0ubuntu1
  Version table:
 *** 42.9-0ubuntu1 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     42.0-3ubuntu2 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
gir1.2-mutter-10:
  Installed: 42.9-0ubuntu1
  Candidate: 42.9-0ubuntu1
  Version table:
 *** 42.9-0ubuntu1 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     42.0-3ubuntu2 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy/main amd64 Packages

And I do hit the error when trying to revert after changing the scale:

Jul 18 09:40:39 U-2RVWD6LKXR3GE gnome-shell[3186]: Failed to use linear monitor configuration: Invalid mode 800x600 (-nan) for monitor 'unknown unknown'
Jul 18 09:40:39 U-2RVWD6LKXR3GE gnome-shell[3186]: Failed to use fallback monitor configuration: Invalid mode 800x600 (-nan) for monitor 'unknown unknown'
Jul 18 09:40:39 U-2RVWD6LKXR3GE gnome-shell[3186]: Impossible to set scaling on crtc 59 to 1.000000, error id 2
Jul 18 09:40:40 U-2RVWD6LKXR3GE gnome-shell[3186]: Xlib:  extension "DPMS" missing on display ":1".


Then, I upgraded to package from -proposed:

user0@U-2RVWD6LKXR3GE:~$ sudo apt-cache policy mutter-common libmutter-10-0 gir1.2-mutter-10
[sudo] password for user0: 
mutter-common:
  Installed: 42.9-0ubuntu3
  Candidate: 42.9-0ubuntu3
  Version table:
 *** 42.9-0ubuntu3 500
        500 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     42.9-0ubuntu1 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
     42.0-3ubuntu2 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
libmutter-10-0:
  Installed: 42.9-0ubuntu3
  Candidate: 42.9-0ubuntu3
  Version table:
 *** 42.9-0ubuntu3 500
        500 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     42.9-0ubuntu1 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
     42.0-3ubuntu2 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
gir1.2-mutter-10:
  Installed: 42.9-0ubuntu3
  Candidate: 42.9-0ubuntu3
  Version table:
 *** 42.9-0ubuntu3 500
        500 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     42.9-0ubuntu1 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
     42.0-3ubuntu2 500
        500 http://sa-east-1.ec2.archive.ubuntu.com/ubuntu jammy/main amd64 Packages
        
And now the error is no longer logged and I can successfully revert:

Jul 18 09:44:35 U-2RVWD6LKXR3GE gnome-shell[3199]: Impossible to set scaling on crtc 59 to 1.000000, error id 2
Jul 18 09:44:35 U-2RVWD6LKXR3GE gnome-shell[3199]: Impossible to set scaling on crtc 59 to 1.000000, error id 2
Jul 18 09:44:35 U-2RVWD6LKXR3GE gnome-shell[3199]: Window manager warning: Scalig CRTC 59 at 1.000000 failed
Jul 18 09:44:35 U-2RVWD6LKXR3GE gnome-shell[3199]: Impossible to set scaling on crtc 61 to 1.000000, error id 2
Jul 18 09:44:35 U-2RVWD6LKXR3GE gnome-shell[3199]: Window manager warning: Scalig CRTC 61 at 1.000000 failed
Jul 18 09:44:35 U-2RVWD6LKXR3GE gnome-shell[3199]: Impossible to set scaling on crtc 63 to 1.000000, error id 2
Jul 18 09:44:35 U-2RVWD6LKXR3GE gnome-shell[3199]: Window manager warning: Scalig CRTC 63 at 1.000000 failed
Jul 18 09:44:35 U-2RVWD6LKXR3GE gnome-shell[3199]: Impossible to set scaling on crtc 65 to 1.000000, error id 2
Jul 18 09:44:35 U-2RVWD6LKXR3GE gnome-shell[3199]: Window manager warning: Scalig CRTC 65 at 1.000000 failed

(The errors above can be ignored for now as their are a known problem with Xdcv, which is further explained in comment #16)

Marking as verification-done