While right now we've seen some KDE efforts around Flatpak (formerly XDG-App) and Snaps along with some in the AppImage space, KDE developers are looking to center their efforts around one next-gen packaging solution moving forward. With focusing around one app bundling solution, they hope to be able to deliver their software to more end-users directly across the distribution spectrum.
So far it appears that they are leaning towards using Flatpak as their primary choice for packaging of future KDE applications. It does appear there is some fondness for Snaps that is led by Canonical, but a comment was made regarding to how Ubuntu is handling Snaps and their centralized approach. Here's what Sebastian wrote:
From a Plasma point of view, we want to concentrate on a single technology, and not three of them. My personal favorite is flatpak, as it is technologically the most advanced, it doesn’t rely on a proprietary and centralized server component. Unless Canonical changes the way they control snaps, flatpak should be the technology KDE concentrates on. This hasn’t been formally decided however, and the jury is still out. I think it’s important to realize that KDE isn’t served by adopting a technology for a process as important as software distribution that could be switched off by a single company. This would pose an unacceptable risk, and it would send the wrong signal to the rest of the Free software community.
So keep in mind no formal decision has been made yet, just for now at least they are leaning towards using Flatpaks over Snaps.
At this sprint there was also work done on native notifications from browsers, better integration elsewhere, etc. More details via this blog post.