I know that this has been addressed before by others but allow me to address it once again. From a topic of a few years old where a user complained about the lack of Linux support I got the strong impression that there are a few big misunderstandings about Linux and the typical Linux user amongst the developers of EarMaster.
Let's start with this. If the support for the Apple operating systems has already been worked out then porting it to Linux should be a piece of cake given that OSX uses a fork from an old FreeBSD version (poorly updated by Apple but that is irrelevant here). Both systems have a lot of similarities and use open source software at its foundation which makes it easy to port from one system to another. OSX is not FreeBSD but it has the same core in the system as an old version of FreeBSD, with an Apple sauce over it for the GUI and extra software. A lack of Linux support should probably be interpreted as a lack of interest from the developers. Probably because they are pessimistic with regard to profit vs. costs. That is fine and well within their right given that they are a profit-driven company, the question here which I adress is how realistic their estimation is. I admit, linux is only being used by 2-3% of the desktop users but Apple is not big either, they are under 10% too, worldwide. In the USA Apple is big, in the rest of the world (Europe for example) they are not, not for desktops and laptops anyway (and for phones Samsung on its own beats Apple in Europe).
In that old thread the responder (employee of EarMaster) pointed out that he had doubts whether or not Linux users would be willing to pay for software. This is a huge misunderstanding. In general Linux users are not freeloaders! As a matter of fact, many Linux users have a background in science and technology, they understand that there is a place for proprietary software and that it costs money for companies to make it. There also are examples where open source software works better than third party software because many experts can contribute and it only keeps getting better (Musescore2 is a good example, take a look at it if you don't know it yet, it also runs on Windows and you don't even need to install it, only download it) but not for every useful application you get a large enough open source communicty of programmers and other people (graphics designers...) to work it out. In that gap proprietary software has a valid place. I myself spent hundreds of € on games (GOG, Steam, even Origin), more than I care to admit.

Why do Linux users prefer Linux? Because they believe that operating systems and APIs should be open source. There are many technical reasons for that (compatibility, freedom, security, privacy, being in charge over your system, generally a better performance...) but I won't go into that in this context. The point is that Linux users are willing to pay for [b]good[/b] proprietary software. As a matter of fact, since that Valve pushed gaming on Linux -with its own games but also by encouraging other succesful developers to port their games to Linux - Linux users spend a lot of money on games via Steam. Most Linux users are pragmatic, they are not against using third party proprietary software and they uses proprietary drivers (even when the distro doesn't support it out of the box, then most users install these drivers themselves, if available), they just want a free operating system and free APIs.
There are many Linux-distros but most Linux users use only a few systems, if you look at the core and you ignore trivial details (which desktop they use...): Debian, Ubuntu (a fork of Debian), Mint (a fork of Ubuntu) and Fedora. Those are the big systems. There are systems like ArchLinux and Manjaro (which I use) but you don't have to worry about that, these communities will get it done for you. Support Debian and Ubuntu and it should work on other Linux distros soon.
Porting EarMaster Pro to Linux doesn't cost much development time. There are many musicians on Linux. Just as an illustration I refer to a popular forum for Linux musicians.
https://linuxmusicians.com
Linux is a good system for musicians. Why? Because you don't have to use a bloated operating system (Windows10, Windows7, OSX) which makes it possible to have a low latency which is desired for recording music. Also there is some great software for MIDI and recording, both free (libre) and proprietary. I myself use Rosegarden to record MIDI (a Yamaha Clavinova 'piano') and Audacity to record analog sound, it works great on the amateur level. Personally I don't bother with Wine for several reasons (time, bugs, not willing to run software less than perfectly), I am only willing to buy Windows-tied software for games, I start those up once upon a time and play those a few hours during some weekends, other free days and holidays. Booting to your Windows partition is doable when you game for a few hours, it is a pain in the butt to do that for running EarMaster Pro for 10-30 minutes.
Maybe it would interesting to partner up with Valve for running this software on Steam in Linux. They have a lot of expertise and they don't take a big cut (10%) while they do boost the sales. It could be a win/win/win (EarMaster/Valve/enduser). I tried out EarMaster Pro and I like it but I won't buy it as long as it doesn't run on Linux.
Kind regards.