Smilebooth's backend runs on mono on linux, but for private / no internet events we run a local version of the server on .net 4.x and windows. Same binary. F#/suave.io server. I was shocked ~5 years ago when I tried the .net binary on mono/linux and it just worked (iirc the only change was the command line arguments passed to imagemagick). But it did and it has, so no need to change.

I left that project two years ago but if starting something similar today I'd probably go with .net core. Not because of any issues with mono, but core just seems like the future. I didn't even realize that mono was still in active development, though I'm not really following that field anymore, so.

Just for the record, I never did notice any memory leaks that others complain about. Our servers stayed running for months at a time with no noticeable leaks.