Nobody is going to support 5 year old Slackware for their game distribution platform. They'll support current Ubuntu and maybe Fedora--anybody else can work out the problems on their own.

And by support I mean a one-off build for the platform and a public forum where users can ask and answer questions of other users. Maybe if you're lucky they'll do a new build when a patch is released.

Linux users aren't asking for much, and Epic has been more than just dismissive to them. They've been outright hostile, doing things like adding checks to make sure the game isn't running under Wine.