Haven’t had landlines in a long time but when I did I remember looking at cordless phones with Bluetooth to connect to your cell phone so you can answer both phones (cell phone and landline) on the handset. Beyond that look into pbx.

Too little too late

Sonarr is TV and radarr is movies.

You didn’t specify but this sounds like an issue where you are confusing sonarr and radarr where only one is configured “properly”.