After upgrading to 22.04, I realized that the wallpaper/background will switch back to default jammy wallpaper when in dark model even after removing and setting it to solid color. This problem doesn't appear while in light mode. I think this is a Gnome related issue?
command line used;
gsettings set org.gnome.desktop.background picture-uri
gsettings set org.gnome.desktop.background primary-color '#000000'
Kindly advise
update
as suggested by @vanadium(thank you), it's the new feature in 22.04. and adding -dark will enable the change. Hence, for those wanting to have a solid black ground without using a wallpaper, just use this command in terminal
gsettings set org.gnome.desktop.background picture-uri-dark ''