Thanks for sharing Manticore! I didn't mention SML# because most of the documentation is in Japanese and it's hard to find recent info. There is an unofficial fork on Github but it explicitly states that it is unofficial so... not something I'd recommend to a general audience.

Edit: nevermind! I checked out their docs again and it seems to be decently translated. I'm still not sure where their code is actually hosted, just that you can download releases. So added it to the list of major implementations!