tomscharbach I distinctly remember, in forum, a dev saying flatpak/snap playing a role in upcoming software center was only at the "discussion" stage, and, like your info, probably years old and it's pure speculation now. May have even been a Strobl-era discussion but I stand by my recollection. The key would be, I agree, autoupdating this stuff via SC, as opposed to manually doing it now.
The problem with this sandboxed crap--and I will start a new thread---especially the browsers, and a GIGANTIC pet peeve of mine is they all lose the ability to spellcheck and underline and access system dictionaries. I don't know how to remedy this and it sticks in the craw. Flatpak on Solus only offers mostly-functional browsers...