https://forum.affinity.serif.com/index.php?/topic/98932-faq-affinity-on-linux/

They didn’t say they never will. They don’t have plans for it, but they won’t rule it out.

We won’t rule out making a Linux version of Affinity in the future if the right Linux distro comes along with a reliable deployment platform that will allow us to recoup our development cost for the Linux version.

I guess they could use Flatpaks here if they don’t want to deal with packaging it for every distro.