Thanks for the PR. Could you please elaborate why you consider these URLs to be relevant here? According to the docs, only the homepage is mandatory and the VCS URL is recommended.

The URLs defined here in the AppStream metadata are i.a. used by package managers to provide direct navigation hints to the respective resources.

If the type="donation" URL is set, Flathub displays a prominent Donate button next to the Install button at the top right (example: Clapgrep).

The rest of the URLs are displayed in a dedicated Links block (example: Flare):

Bazaar uses these URLs similarly.

The link back to GitHub also resolves a linter warning at @flathub which they claim may become an error at any time. https://docs.flathub.org/docs/for-app-authors/linter#appstream-missing-vcs-browser-url

I do not feel safe enough here to decide whether all of these values make sense for DB4S. Thus wait for a second opinion from the team here.