Possibly after the update from 21.04 to 21.10, the standard GNOME editor gedit started not displaying the background grid pattern.
I tried to unset and set the Display grid pattern setting from gedit's Preferences / View tab: Nothing changed. (All the other options -- except this one -- work as expected.)
Using dconf-editor, I tried to change org.gnome.gedit.preferences.editor.background-pattern attribute to 'default', 'none', and then back to 'grid': Nothing changed.
Similarly, running the commands gsettings set org.gnome.gedit.preferences.editor background-pattern 'none' and
gsettings set org.gnome.gedit.preferences.editor background-pattern 'grid' has no effect.
I tried to remove ~/.cache and ~/.config/gedit: Nothing changed.
I tried to login with Wayland, XOrg, etc. Also, I tried to change themes using gnome-tweaks: The problem stays the same.
On another (rarely used) user on the same system gedit works as expected: It displays or hides the grid depending on the selection Display grid pattern in Peferences / View tab. I am also able to change the "grid pattern" for the root user, after running sudo -H gedit for example.
This problem seems to be present only on my "main" user.
The Applications Theme I use in my current user is "Adwaita (default)" and it is not a dark theme.
The Color Scheme in gedit is "Yaru".