My feeling was that Microsoft open sourced the .net framework to help Mono catchup a bit.

As for access to windows, to be honest I think that's pretty easy to have. Run on general purpose hardware, it's not that expensive.

I think that having access to a Mac is relatively harder than having access to a Windows machine.

When .net core came out I was under the impression that the product was the future of .net but maybe I was living in a bubble.

Anyway, I understand your point but I still think that the disinterest towards .net is tied to a generalized adversion to Microsoft (probably deserved) but not really related to the tech itself nor it's availability on Linux or Mac.