Graphic designers mostly use the Gnome 3 (GTK 3) desktop environment on Linux. Afaik the Gnome people are trying to make it easy for new devs (Gnome builder app etc.), and their preferred distro of choice, Fedora (RedHat), even has it's own spin focused on design, Fedora Design Suite.
https://wiki.gnome.org/Apps/Builder
Some months ago i read that they (Fedora) are trying to appeal to commercial 3rd party app developers too, to bring them into their appstore. This is something worth investigating i think.
I have used Linux exclusively in the last few years as my main operating system, and got my first Mac recently to try out the Affinity products and other apps for design, mainly logodesign and lettering, having a background in street art myself.
While you can work and establish a "professional print workflow" with the open source design apps on Linux, the problem is more the different UI paradigms switching between apps, which makes it very hard to learn if you're not focused only on one design topic.
That's what's missing on Linux, and the big advantage of the Affinity products, apart from not beeing limitied to free open source formats and all the restrictions from that.
A future dream would be a Affinity Linux distro, like a commercial spin/fork of Fedora with the Gnome 3 interface themed like the Affinity apps. Similar to what Valve is doing for Gamers with SteamOS. I think that there is a lot of potential.
