Mp3tag is available on Windows, macOS, and Linux (via Wine). To help clarify which platform is being used, I've introduced a new mandatory profile field for the Operating System.
This should make it easier for everyone responding to support questions, bug reports, and feature requests to determine the specific Mp3tag variant in use.
Additionally, you can join the user groups — Windows, macOS, and Linux. If you haven't been auto-joined during registration or added manually, you can join (and leave) yourself. These groups also allow you to set an avatar-flair icon via Account settings, that's displayed next to your profile picture.