If you’re looking for EQ apps for iOS and macOS...
Radsone has a nice player with a very capable EQ built-in:
https://apps.apple.com/us/app/radsone-hi-res-player/id917903045. It’s what I use to correct the stock sound signature on the XM3s, and it works extremely well. I know others here also recommend the Onkyo app on iOS; based on my limited experience its UI is a bit more complicated compared to Radsone’s. Both only work with non-DRM’ed media.
On macOS, I like using the Music app’s built-in EQ. I know others like Audirvana and Vox.