From the description of "R | Diamond API", I believe you will almost certainly be considering to be operating an ATS if you're using it. CME almost automatically treats you as a firm/professional if you are operating an ATS and applies non-display fees.
You don't have to spin up a Windows VM if that makes you unhappy. You could achieve a platform-independent setup if you used a browser-based GUI, which some members on the forum seem to have gone down.
Just a hint, you almost certainly don't want to compete in the "low latency space" with a "tick-to-trade of 250 us". I'm not saying this to deter you from doing what you're passionate about, but rather to save you thousands in development costs and vendor fees only to hit a barrier when you've finally made it, which is both demoralizing and great for the vendors but bad for you and the market. This is of course not something your vendor will tell you.