You could try the Dark Mode Wallpaper app, from the Droid AppStore or from Github https://github.com/cvzi/darkmodewallpaper I use it on my Samsung Phone to change the wallpaper and it should work without the gallery app.
You could try the Dark Mode Wallpaper app, from the Droid AppStore or from Github https://github.com/cvzi/darkmodewallpaper I use it on my Samsung Phone to change the wallpaper and it should work without the gallery app.