It’s up to the distro maintainers to package it for the distros. Not the software developer. I see it’s available in the AUR, so it’s not only available as a flatpak. So ascii.-draw does fit your criteria.
You can also build it yourself if you know how (they list the use of gnome-builder for this).
Only reason I got it, was because it was cheaper than the Red Hat one and my employer just needed me to get a Linux certificate. So the cheapest was what I got.