They could at the very least just package it up to run with Wine, but Sweeney is stubbornly set in his linux hating ways. I could use their store through the Heroic launcher, as I do with GoG, but I won't because fuck you Tim.
If we're being realistic from a business standpoint: Linux is at best, 3% market share. A very passionate 3%, but 3%. Using resources to support such a niche sector is a hard sell.
3% of millions of people is a massive number of people. Given how easy recent work on wine has made porting from windows, it's really hard to defend not having a linux version, from a business standpoint.
I'd hope this community of all places would understand that "just integrate X with Y" is never as simple as "just". It's still something a team needs to do, and the gain is minimal unless Epic is also going to try and make their own console-esque device. That's the incentive for Steam.
It's a glorified wrapper around curl, wine and a webview, a few interns could knock this out in a few months. For "3% market share" (growing every day, thanks to Valve) its a no brainer, but Sweeney has no brain.