Can I post about Mihon here?

Sure!

As for sources, almost my entire library is Mangadex with just a few exceptions. I have a couple Manga Plus series that I follow, one VIZ series, and then the odd scanlator group here or there that posts things to their page way before Mangadex and have an extension.

But seriously though, I just ran the numbers and I am at ~95% Mangadex.