When I open the downloaded file I get an error: The requested file \FiraCousine.ttf is not a valid font file. Same error with the bold version.
I'm on Windows 10.

I just installed Cousine (looks a lot like JetBrains Mono, or maybe other way around) but had no ligatures and that's when I found this repo. I too found FiraCode too curly but gotta love those ligatures. Your font would be so perfect but I can't install it. Any idea what the issue could be?