sure, and convince people to switch. it’s been done before of course but it’s a big effort

I agree! But this, IMO, is a better argument for how flathub.org being (theoretically) open source doesn't actually make it any better than snapcraft.io. The technical hurdle, either of writing another snap store or of setting up a flatpak host, pales in comparison to the social hurdle of getting people to switch. Which is likely why the previous open snap store implementation died. Nobody wanted to host their own and convince people to switch, because at the end of the day there wasn't any benefit.

that does not mean that the particular developer agrees with or even approves of the snap thing.

Never said it did, although in the particular case of the developer I mentioned, he's also an Ubuntu Core developer, which depends entirely on snaps. I can't imagine he'd have put himself in that position if he were particularly anti-snap

steam was a big one that a friend had trouble with, and they just installed that though apt i’m pretty sure.

Ubuntu has never had a steam package in their apt repos, and the steam-installer package still behaves the same way as ever. Personally, I do use the Steam snap and haven't had any issues with it, though I do know that others have.