Companies like the one I'm working right now is changing to Linux not because of the cost, but the security and easy integration with cloud stuff. At the beginning I resisted a lot to change from Windows to Linux but in the end it happened like they said to me when I finally changed: "It's just as usable as Windows and MacOS. You will only miss Photoshop." And indeed it's being like this. There is no good option to replace Photoshop. They are barely usable.
I'm not a full time designer, but I have to fix some images several times a day and tasks that usually take a few minutes now takes several minutes and sometimes hours. It's not just my inability with the program, it's the way things are made. Sometimes you have to go to several weird (and not intuitive at all) steps to accomplish simple tasks you make in a click on Photoshop or Affinity Photo. It's a nightmare.
Affinity is by far the best alternative to Photoshop. For some tasks is even better. I know, as a developer, that when people say: "make a version for Linux" is not that easy to do because you don't have just one single Linux distribution. You have literally thousands of them. They differ from each other by a lot and even though they are based on a few major distributions, they are still very different in terms of how the binaries are treated at SO level.
But today, there are some projects to make this easier and the most popular is the Snap project (https://snapcraft.io/). It's made by Canonical and supported/used by Microsoft, Google and Jetbrains (to name a few). It consists in tools and an integrated platform to make publishing things to Linux easier. There are free and paid software there and you can install things with a click, which makes easier for non-developers. Maybe Affinity for Linux can be a viable option right now because of this.
Summing up, Affinity products for Linux would be the best option in the platform with no competition at all, and companies, not just users, may be interested in purchase Affinity licences for their artists.