@HerraBRE I would say snaps, but I'm an Ubuntu member. And I worked on Snapcraft for a while.
The big reason is that even though Flatpak exists in my distros it's not setup with repos by default. So users still can't find your stuff.
@HerraBRE it sounds like you're thinking about them as packaging formats, which they are, but that's not the most interesting part. The biggest change is converting to a confinement model for your application. It puts a lot of pressure on developers for a huge user win, though developers get wins too in a more direct access to their users.
For instance, you can make a snap from a deb really easily. But it may not work.
Also, I don't expect my next Ubuntu desktop to be able to install debs.