Proprietary snap store backend that is controlled by Canonical: that's it.
I used Ubuntu for years: installed it for family and friends. I moved away around a year ago.
Moving packages like Firefox to snap was what first started annoying me.
If the backend was open source, and the community could have hosted their own (like how flatpak repositories can be), I might have been slightly more forgiving.
Did a quick Google to find if someone had elaborated, here's a good one:
Do the three finger swipe left and right to switch desktops.
Then three finger swipe upwards for overview.
It'll be Gnome all over, I promise you!