Something I would like to be able to do: mirror all my issues that I own from across various code forges (Github, Codeberg, etc.) into a single list of my choosing, for example, as an RSS feed or a Markdown list or whatever.

Actually, as RSS feeds this already works (one feed per forge).

But what I have in mind would go further than that. Ideally, any tags associated with each issue should be visible, and full-text search should be possible. Also, the list should clearly indicate closed issues as such.

The point is, to have a single place to check to remind myself of any issues I have opened. This kind of mirroring would also insulate you from short-term service interruptions on the forge, assuming the project in questionn is still available locally (which it always is, thanks to git). But moreso, this would also help as a sort of backup in case the forge went away completely (say Github gets sold and scuppered, or whatever).

I am considering this today because I just spent the better part of the afternoon moving, manually, "tasks" from my Nextcloud instance to their proper place as issues on my Codeberg repos.

I don't know how to achieve this. I am pretty sure it needs to involve authentication to each forge. Is anyone aware of some existing work in this vein?