@VectorStyler nah, it's mostly dead. All modern desktop environments are focused on first-class Wayland support. GNOME already dropped X11 support completely, KDE will drop it by the end of the year. Many new popular tiling managers like Hyprland or Sway are Wayland-native from the start. Older ones like Cinnamon and XFCE are actively working on Wayland support, but they are not as popular as they were in the past. Modern Ubuntu by default ships just its own flavor of GNOME, if you missed that part.
Overall, a major part of Linux users still split mainly between GNOME and KDE. KDE recently has gained more popularity since SteamOS adopted it, and overall development has sped up.
Also, there is a big surge in so-called atomic or immutable distributions: those have a fixed system image that is immutable; you cannot install or uninstall system packages, remove your DE accidentally, or mess up the dependencies. The only things you can change are config files and your /home directory. The main source of apps for those distros (e.g., Fedora Silverblue/Kinoite, Bazzite, SteamOS, etc.) is Flatpak and Docker/Podman containers. Basically it is similar to how modern smartphones function.
So, again, with Flatpak you would cover both immutable and basic distros. By default, the Flatpak platform is not installed on Ubuntu, because Canonical has its own similar technology called Snap and its own store called Snap Store, but it can be easily installed using one command, though it usually makes sense to upload to both Snap Store and Flathub. If resources are limited, Flathub is preferred, since Snap support outside the Ubuntu ecosystem is questionable.
From a developer's perspective, the key difference between Flatpak and Snap is how applications are distributed. Flatpak allows anyone to host their own repository, while Flathub serves as the default public repository. Snap, on the other hand, relies on Canonical's Snap Store, and developers cannot host their own independent repositories.
