Developer at XDA called 'iaTa' explained how the pack of live wallpapers that ship with the OnePlus 7 Pro can be applied onto older OnePlus devices, provided they’re running OxygenOS. At the end of the post, there are four APKs that make it easy to install the Live Wallpapers.
There will be four individual APKs instead of regular one APK wallpaper package. Try the repackaged APK files for yourself and let us know in the comments if any of the four files (the blue, gray, gold and red wallpaper packages) work for you!