@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.
@ted @HerraBRE You can host the flatpak file on your site as they're really small (libreoffice is only 3.9kb) and have it point to flathub or another repo.
Even if you are sand boxed in you still prolly have you Downloads folder exposed if you need to download something. You should just be able to click on them and let Gnome software or Discover install it from there.
@squeakypancakes @HerraBRE I don't know stats, but I imagine the number of people that have the flatpak handles for websites to be really small.
For instance, that wouldn't work on my machines because I use the upstream Firefox snap and it can't install stuff in my machine (a good thing).