Set the score for your "x265/HEVC" format to a positive number (e.g., Ensure your Upgrade Until Custom Format Score
This is the phase where you auto-replace your old x264 files. sonarr prefer x265
x265 is a mathematically denser codec. Many client devices (smart TVs, older streaming sticks, tablets) do not have hardware decoding for x265. When this happens, your media server (Plex, Jellyfin, Emby) must transcode the file on-the-fly to a codec the client can play—usually back to x264. Set the score for your "x265/HEVC" format to
Optimizing Sonarr: How to Prefer x265 (HEVC) Content Sonarr is a powerful older streaming sticks