I always found it interesting that no professional-level layer-based image editor/compositor is available natively on Linux systems in spite of Linux playing a very important role in Visual Effects, 3D and (high level) film compositing and editing. Software such as Nuke, Houdini, Maya, etc. are all there, (support for 3d and high level compositing and VFX work is arguably much better on Linux than on the Mac platform) and I heard and read about how large film studios maintain a couple of Windows or Mac systems with the sole purpose of running Photoshop to prepare assets for import.
But perhaps the complexity of the work at high-end studios and the relatively tiny designer user base explain why so far nothing (outside Gimp and Krita) has appeared for the platform: on the one hand the complexity of production-level VFX and compositing work automatically means that a layer-based approach is just not feasible (requiring node-based compositing and VFX), and the lack of powerful animation controls only exacerbates this, while on the other hand the lack of professional designers working on Linux means most users never leave the confinements of relatively simple image editing work (for which Gimp more than suffices and is steadily improving).
Gimp is becoming good enough now with the addition of 16bpc and 32bpc (and the upcoming adjustment layers), and digital painting is already catered for with Krita. And if you are working as a 3d artist or compositor your primary tools and workflows wouldn't care much for a high-flying image editor, because excellent production proven tools already are available. As a 3d artist I probably couldn't care less about the presence of Affinity Photo on the Linux platform (or even on Windows and Mac) when I have access to Substance Painter and Designer for my texture work. I'd be heavily invested in those tools, and for the odd simple image editing I'd probably just get something free like Krita or even Gimp.
Hence, no real user base exists on Linux that would invest money in a commercial layer-based image editor. Corel tried, and failed. It turned out to be not feasible.
So as a commercial company like Serif and Adobe, I'd think twice before committing a lot of human resources and money down a potential rabbit hole with little or no return on investment. And honestly, I just don't see those few independent professional linux-based artists leave their tools for a less powerful tool (for example, David Revoy works in Krita, and whether you like it or not, Krita surpasses both Photoshop and Affinity Photo in regards to digital painting). And besides, many of these artists and designers tend to be advocates for open software, and probably wouldn't give commercial software a second glance, if even a first glance. It's not part of their style or life/work philosophy.
On top of all this another concern for commercial vendors of software: when I install Linux Mint on people's machines (like my wife's :-) ), Gimp and LibreOffice are pre-installed, ready to play. Installing other graphics software is just three clicks away. I don't see the average user clamouring for Affinity Photo when they can immediately open Gimp to do some simple image editing, or install Microsoft Office. Unless you'd be a professional 3d artist/film compositor/VFX artst and have need of Nuke or Maya or Houdini or etc. - but those professionals on Linux work in very different industries, and certainly not in the print industry. They couldn't care less for Affinity Designer, for example. Designer wouldn't stand a chance anyway on Linux, not with competing products such as Gravit Designer (and which is available for free too) carving out a niche on the Linux platform.
Mac is a completely different ball game, despite the smaller user base: most professional designers and print involved people work on Macs, and the user base for a product like Affinity is just... there. It exists. In particular with disgruntled Adobe users grasping at the opportunity to leave the Adobe ecosystem, even if the tools aren't that strong as the Adobe ones. From the moment when I first saw Serif's marketing, and how it was aimed at the professional groups of Mac users in the existing graphic designers and photographers communities, I knew Affinity would sell well and become a success. It would be impossible to generate that vibe amongst Linux users. It's a very different user base, and the two are living in worlds far apart.
I would like to see products like Affinity Photo and Designer on the Linux platform, but when I think about the target users, I just don't feel there's much chance of landing many new users to sell the products to. Photo might make a few hundred sales, but Designer? No chance. All in all, not a lot of money-making potential.
