Finally got it set up, pointed Prowlarr at it which synced to Sonarr and Radarr, not readarr or lidarr though. I couldn’t manually point readarr at it either without getting a

Query successful, but no results in the configured categories were returned from your indexer. This may be an issue with the indexer or your indexer category settings

which is a shame. Still a potentially powerful bit of kit regardless.