It’s not super hard to leave Spotify if you are willing to invest some effort.
Use Exportify (free service) to download his playlists from Spotify as csv files. Or use something like Soundizz (paid) to directly convert between platforms.
You can parse the csv files and use something like Soulseek to create an offline library. Compress to aac or opus so you can take thousands of songs with you on your phone, or use your own casting service on a raspberry pi.