> but devices like the Steam Deck prove that mobile linux isnt as much of a problem re: userspace as you claim.

So.... by relying on yet another company with multiples of $10B in revenue who spent a lot of time and money to build (and maintain) an entire custom frontend/compatibility layer to provide a stable UX for managing apps without intimidating non-tech savvy users? Where security isn't even a distant priority as it's a restricted store in a proprietary walled garden exclusively for games (and not your banking app or crypto wallet or browser tabs)?

SteamOS, very similarly to Android, entirely depends on a corporate benefactor leveraging a parallel user space that happily bypasses the "normal" community-supported parts of a typical Linux desktop distro wherever they present an obstacle. It proves that a company with deep pockets could indeed create a new mobile Linux distro (by writing lots of checks and cutting out large chunks of desktop Linux in favor of custom implementations entirely under their control).