You can install yt-dlp and run a script to download the playlist and convert to MP3. But if you don't need to be in MP3 format, you can take a look at tubearchivist. It'll download the videos from the channel, playlist or just the video. It'll keep a log and doesn't redownload the same video.

You can check out awesome-selfhosted listed of softwares and see what you're interested in looking to self host. Common things to self host is a media player that host your movies/TV shows/ or music. A Google drive replacement like nextcloud. Another idea to look for is, whatever services you're using already , see if you can self host that yourself and see where that takes you.