How do I make System monitor use the same theme as Ubuntu 22.10 Cinnamon 5.4.12

Question

Ubuntu 22.10 with Cinnamon desktop 5.4.12 not showing System Monitor 42.0 with same theme:

Ubuntu release updated yesterday 3th november 2022 from 22.04 using lightdm and Cinnamon to Kinetic.

I didn't found any settings to allow to change it:

How can I make it use the same theme?

I found the same question here, on github, but the problem came from the snap version.

I installed it with apt install gnome-system-monitor:

My current theme settings:

I found the same issue on Github with another theme. It seems it's gnome-system-monitor that does it wrong with GTK4. Here another article: https://www.phoronix.com/news/GNOME-HIG-2021-Design describing they are bussy with the implementation of it since 2021.

Is there no workarround solution since ?

I made other tests, and it seems gnome themes only are provided with GTK2 support. Am I right?

root@lubuton:/home/wingarmac# apt-cache search gnome-theme
gnome-themes-extra - Adwaita GTK+ 2 theme — engine
gnome-themes-extra-data - Adwaita GTK+ 2 theme — common files
gnome-theme-gilouche - openSUSE Gilouche Theme
gnome-themes-standard - Adwaita GTK+ 2 theme — engine - transitional package
gnome-themes-ubuntu - Ubuntu community themes

So I can presume it's because gnome-system-monitor isn't GTK4 compatible?

If so, can I make it use the dark GTK2 theme instead eventually ?

I also tested the installation of the snap version:

root@lubuton:/home/wingarmac# snap install gnome-system-monitor
gnome-system-monitor 42.0 from Canonical✓ installed

With same results for both described as follow in the Cinnamon menu:

(I do not know which one is snaps so I tried both)

These tests where all made on my personal computer till now. So I've another computer for test, where I did install Ubuntu server 22.10.

After the installation of it:

sudo su
apt update && apt upgrade
apt install ubuntu-desktop --no-install-recommends
apt install cinnamon
apt install ubuntu-mate-icon-themes
apt install nvidia-driver*
reboot

After logon I've configured my desktop like on my personal computer with the Adwaita dark theme and Yaru red icons. gnome-system-monitor shows up in dark.

Other sites visited (information - sources - similar issues):

• How to set dark/light mode from the GNOME session in Ubuntu 22.04?
• https://manpages.ubuntu.com/manpages/focal/en/man1/gnome-session.1.html
• https://www.phoronix.com/news/GNOME-HIG-2021-Design
• Gnome-System-Monitor has no GTK Window Decoration
• https://github.com/dracula/gtk/issues/127
• https://www.reddit.com/r/gnome/comments/tbqydi/gnome_42_dark_mode_not_applied_to_every_window/
• https://gitlab.gnome.org/GNOME/Initiatives/-/wikis/Dark-Style-Preference#other
• https://www.geeksforgeeks.org/how-to-install-adwaita-icon-theme-on-ubuntu/
• https://github.com/ubuntu/gnome-shell-communitheme/issues/87
• https://snapcraft.io/gnome-system-monitor
• https://github.com/ubuntu/yaru/issues/296

Answer 1

After some tests I found a solution.

I first took a look to the Cinnamon System Settings in de menu.

It was wrote as comment "Control Center".

Since gnome-system-monitor is from gnome I search for the /bin/gnome-control-center on my current install. I found it and tried to open it:

From there I could set the dark appearance:

After that the gnome-system-monitor was also with a dark theme:

I installed the apt version instead of the snap version of gnome-system monitor, since the icon in the taskbar is the last version of it , what wasn't the case of the snap version.