Just to pick a nit that may lead to confusion when discussing this topic.
“Apple Music” is an on-line streaming service, similar to the paid-tiers of Spotify and Pandora.
The macOS app that replaced iTunes is just “Music”. As is the mobile iOS/iPadOS app. I often call it “Music.app” (the macOS package’s file-name), to make it less ambiguous.
Where it can become particularly confusing is that Music.app may be used as a player for streaming content from Apple Music, in addition to playing content from your Music.app library.
I’m not trying to change your mind here, but I’m curious about the reason. These days, AAC is a pretty common audio format and is supported by more than Apple’s ecosystem. It’s actually an MPEG standard, just like MP3 is (neither of the "A"s is for “Apple”). And it gives better sound quality for any particular compression ratio.
Although some AAC files (especially first-generation iTunes purchases and streamed content) are DRM-protected, DRM is not a mandatory part of the file. Later-generation iTunes purchases and content you rip yourself will have no DRM.
Of course, if you are using players (software or hardware) that are not compatible with AAC, then ignore everything I wrote above.