I thought I could offer help here as I often use this
https://api.github.com/repos/:owner/:repo/releases/latest myself to get the latest release of a repo.
But it fails also.
Maybe this is to do with it being an organisation? But then tags work fine!?!
The tags JSON isn't easily sorted, I can see that. Maybe a good old fashioned web scrape of the releases page, and take the first element in the list? Not ideal.