Gnome wallpaper changer in native systemd user units

play-wallpaper.yml

#!/usr/bin/env ansible-playbook
---
- hosts: localhost
  become: false
  gather_facts: false
  connection: local
  tasks:
  - name: Systemd user config location
    file:
      path: ~/.config/systemd/user/
      state: directory
  - name: Wallpaper service
    copy:
      src: wallpaper.service
      dest: ~/.config/systemd/user/
  - name: Wallpaper timer
    copy:
      src: wallpaper.timer
      dest: ~/.config/systemd/user/
  - name: Enable wallpaper timer
    systemd:
      name: wallpaper.timer
      scope: user
      enabled: yes
      state: started

# vim: filetype=yaml

wallpaper.service

# ~/.config/systemd/user/wallpaper.service
[Unit]
Description=Wallpaper Change
StartLimitIntervalSec=0

[Service]
Type=oneshot
Environment=wpdir=%h/Nextcloud/Wallpapers
ExecStart=/usr/bin/env sh -c 'gsettings set org.gnome.desktop.background picture-uri "file://$(find "${wpdir}" -type f | shuf | head -1)"'
ExecStart=/usr/bin/env sh -c 'gsettings set org.gnome.desktop.background picture-uri-dark "$(gsettings get org.gnome.desktop.background picture-uri)"'
ExecStartPost=/usr/bin/env gsettings get org.gnome.desktop.background picture-uri

wallpaper.timer

# ~/.config/systemd/user/wallpaper.timer
[Unit]
Description=Wallpaper Change Timer

[Timer]
OnStartupSec=60
OnUnitInactiveSec=900

[Install]
WantedBy=default.target