The "Users by distribution" table at the bottom of the Spotify page is worth a look:
https://snapcraft.io/spotify
Snaps are not Ubuntu-only. You can find install instructions for many distros here: https://docs.snapcraft.io/core/install
Snaps are not Ubuntu-only. You can find install instructions for many distros here: https://docs.snapcraft.io/core/install
On the other hand,flatpak is a freedesktop project, done using open standards like OCI and ostree.
There is room in the world for flatpak and snap to co-exist. We created snaps as an evolution on from clicks on the Ubuntu phone, and it covers use cases that flatpak wasn't designed for.