I am managing my whole music with iTunes/Musik on a Mac (i will change to Swinsian shortly, I think). I have a few iOS/iPadOS/tvOS/macOS devices that are using the music.
Then I have also LMS and my car which are using the same music (parts of it).

iTunes/Music writes tags named "COMMENTS:ITunNORM" with volume correction into the files. These can be interpreted by all Apple devices.
Then I am using MP3Gain which writes mainly the "REPLAYGAIN_TRACK_GAIN" tag into the files. This is interpreted by the world outside Apple and I hope by LMS and my car.

Does someone here know if the Apple devices also interpret the "REPLAYGAIN_TRACK_GAIN", so I can stop writing the "COMMENTS:ITunNORM" tag? Or do I have to use both of them?