Some further context on this that @Dop@lemmy.world might want to know:
While Canonical's snap store is proprietary (which, to be clear, I don't really like), all the client software is open source and the API is well documented (though a bit janky). Their snap store relay app (which is open source) has a full implementation of it. There was a fully functional open snap store for a while, but the project died out of a lack of interest. You can also distribute snaps through another mechanism and install them locally on the machine (though you then lose the benefit of snapd's auto updates). You can even do this with snapd still checking the signatures of the snaps.
The standard for snaps is fully open, as is snapd itself.
There's no need to oversell the negatives to the point of being wrong.
