At no point was I unable to open the file. The initial problem was that I wasn't able to find the file, because it had the wrong name. And as I said in my initial post, I took a guess at what could open it once I noticed the file was there. Turned out notepad could. Have I done that before? Who knows. I don't keep track of every time I've had to deal with less familiar file formats, nor which operating system I had to deal with them on. It's very well possible I did so when I compiled the dependencies needed for the current custom C++ wrapper I've been using around SDL2. I just checked and one out of nine of them had a "README.md" without an accompanying "README" or "readme.txt". I guess that's not zero.
More importantly, have you actually read that file?
I didn't come here to complain, nor to call the engine "worthless". I came here to point out something that this game development tool failed to do that even less developed tools managed to do: be helpful.