Apple Music lets you add your own files and will automatically sync them to the cloud so you can access them on your other devices. Then you get the convenience of streaming but you can also maintain a library of music you own (or “have acquired”, let’s say).

You’ll need to convert FLAC to ALAC with e.g. ffmpeg or XLD, and cloud files played on other devices will be converted to AAC, but it works really well overall.