The original thread is for Pixel 3 wallpapers on a Pixel 7 Pro, but I used it to take a Pixel 4a (5G) wallpaper to a Pixel 8.
Install WallMan (site). Alleges it is also available on F-Droid. Source code. Wallpapers should remain even after uninstalling wallpapers.
I have saved a copy of the APK onto the Internet Archive, here.