Hey guys, I'm a Junior Game Environment artist and I really don't see why this hasn't happened till now. You just need to put up a page saying the amount of money needed the port Affinity to Linux. I'm an Arch Linux user and I love using Linux a million times more than Windows. I honestly don't see how any Linux lover won't want to pay ONCE for Photo and Designer. I know for a fact that so many Windows users will switch to Linux after Affinity drops.
Right now, us 3D artists are bound to use Windows for our work, when we know that Linux is so much more performant. Blender3D is now gaining a lot of popularity in 2019 and this means a lot. You can see that just the fact that more people are switching to Blender has gotten them more financial aid in just two years of the Blender 2.8 project. As more and more people are trying to free themselves from Autodesk for Blender, others are trying to leave Adobe for Affinity. It might seem one-sided here, but I'm really loving the idea of a future when I can use Blender, Affinity Photo and Designer, Unreal Engine, Substance Painter, Designer, and Alchemist, PureRef and XNormal for game development.
I get that it will cost a ton to make this happen. If you can't port it without financial aid, all you need do is put up a page about it and you'll see just how many people have been waiting for this. The community will spread the word is you take a step forward!