Why is there a need for a 'Linux' storefront. The front-end should be web and OS neutral.
We have moved far beyond "store-front". Modern gaming platforms like Steam or EGS are expected to support a wide variety of in game things including matchmaking (implies external friends list, which implies a social media structure like chat, ideally as an overlay so it can be accessed from within the game) along side a world of other management tasks, such as mod management, update management, achievement management, and that's before you look at things like providing a universal input API to expand hardware support like SteamInput.
Epic did launch "just a store front" and were widely criticised for it.
But they have one thing going for them, their store front is just a web front end. That's actually the biggest criticism. Their damn Electron powered shitshow is an insane resource hog sitting in the background of a gaming session.
No we need to move away from god damn web front ends. Unless you're displaying basic images and providing just a download link, native code a damn app.