I know this was 2 years ago, but for those curious and not seeing the time that passed as an answer... this piece of software was developed somewhere around a decade ago when Marmoset was experimenting more with their products. Their 3D Dev stuff was always the money maker, and so that's where their development and support continued to be focused.
Marmoset Hexels 3, from a professional standpoint, is "complete" as a product version, and for "pay once" software continued development isn't common.
Hexels 3 also came from before it was becoming common to do ANY Linux support, let alone the Steamdeck / Steam OS that made it more important for gamedevs to pay attention to linux compatibility.
I run a dual boot system myself, and would love if Marmo Hexels 3 could easily be run in linux... it probably can via some mixture of compatibility tools. It probably wouldn't be as hard as running Clip Studio Paint.
Alas, since this program isn't popular, and is even less known / more niche today, there's probably not any tutorial videos online.
I might take a crack at it, as I keep wanting to get back to Hexels 3