I doubt anyone of importance will read this but I'd like to chime in and say I use GNU Linux nearly exclusively. I'm not a developer and if anything the install process was easier than windows. I just use it for video editing and "normal" computer usage. I do my photo editing in photoshops webapp and draw vectors in inkscape. I'd drop inkscape and photoshop in an instant for affinity, so just know there is a customer base.
Also to those that seem to be bashing the idea, it's a good idea for more platforms to be supported. AFAIK no pro image software has tried to sell itself on GNU Linux so it is a tricky thing to compare I get, but I can't really see it being a net loss for the company, compiling wouldn't be too hard because it is afterall the same hardware. I mean if davinci can do it I believe in affinity!