Look at the LiveSync plugin as another option. It’s pretty robust but does require a CouchDB server accessible to whatever devices will be syncing information. The developer has several repos of slightly different server options, but if you use Tailscale there’s one that runs CouchDB through Tailscale Funnel.

That is a cool option I hadn’t thought of trying.

But they can pull different quality profiles based on your list preferences right? I don’t see why you need one instance for downloading 4k and one for 1080p.

Can you elaborate on why you’d need two instances of radarr/sonarr running at once?