I seem to recall there's a standard API that should be common to all the #StatusNet derivitave servers. I'm pretty sure that in its infancy Mastodon conformed to that API. But Mastodon's API expanded beyond that, and I suspect some of the common API was removed, probably around the time #OStatus was dropped from Mastodon too.

But that's sheer speculation on my part.

Time to upgrade my server, so I can upgrade PHP, so I can upgrade this GNUsocial instance...