Lossless Audio
Does Apple Music automatically update existing music in my library to lossless audio files?
iPhone 12 Pro
According to the FAQ section in. this article:
About lossless audio in Apple Music - Apple Support
Can I redownload my iTunes purchases in lossless?
If you subscribe to Apple Music, you can redownload music in lossless only from the Apple Music catalog.
And see the 'How to turn lossless on or off' section also.