When a project doesn’t publish a deb or other native package, or when the flatpak is much newer and has features you need.

I like the approach Pop OS takes. Their software store lets you choose between deb or flatpak when you install software. I’ve had issues with flatpak versions of some software, and flipping to the deb package usually fixes it.

I run a static site using Hugo, Gitea, Gitea Runners, Cloud Front, and S3.