How are you on patches no accepted by upstream? There is a patch to fix the recognition of _NET_WM_DESKTOP windows in i3 but the upstream didn't accept it. The patch is required for wallpaper apps to work such as lwp, Plasma Desktop's wallpapers or pcmanfm.

The original PR and discussion can be found here: https://github.com/i3/i3/pull/1828

I rebased the patch against next and 4.22: https://github.com/Thaodan/i3/commit/39fd7e9f6fc649fb1c5a4e112e1dc62ae2bc0170 https://github.com/Thaodan/i3/commit/d2b7bc7ce5c5e8de1dae4a4181bfaa07d760ee0e

I have the patch file in my obs project here: https://build.opensuse.org/package/show/home:Thaodan:X11:windowmanagers/i3