@HerraBRE #Mastodon works with !GNUsocial as it is pretty well. There were some issues that @gargron raised with me, some of which I believe I fixed and some that I couldn't really figure out (some profile avatar update thing for example?)

Regarding RFC7033 (#WebFinger) it - since standardisation - only _requires_ a JRD (application/jrd+json). application/xrd+xml is just a bonus from !GNUsocial (voluntary according to spec).

The host-meta XRD is XML that because it was standardised before people who reinvent everything (JSON fanpeeps) started developing standards: https://tools.ietf.org/html/rfc6415

But since JRD and XRD are easily translatable between each other it doesn't really matter. And while #Mastodon doesn't use it, the /.well-known/host-meta endpoint is good for discovery unrelated to profiles, such as #OAuth endpoints etc. (so clients can auto-configure them).