I don't see how it would be possible, the *arr apps would need to communicate with eMule via RSS feeds or API feeds to be able to query/receive search results. AFAIK eMule does not offer either of those (?) But maybe it's possible if there's a website with eMule links that also offers RSS or API access for the *arr apps.

Also.. I think you're saying that you want eMule to act as both a source and a downloader in the *arr apps, right? It wouldn't do you much good to find a eMule link and then send it to a usenet downloader.

You could try bringing it up as a feature request in their discord / GitHub pages though I'm not too sure how that would work offhand.

• https://discord.sonarr.tv/ and https://github.com/Sonarr/Sonarr
• https://radarr.video/discord and https://github.com/Radarr/Radarr

What you can do is add the eMule download directory as a Usenet Blackhole. You'll still have to start downloads manually in eMule, but radarr and sonarr will pick them up automatically.