Ejabberd external auth
Akkoma bot for Ejabberd
Another easy to use option is to run a bot on your Akkoma instance that can be interacted with to register accounts via the Ejabberd API. You can find the necessary bot software here. The this bot also has some other nice functionality to get details from Ejabberd, so it might be worth running even if another account integration method is used.
If you are setting up a new Akkoma or Pleroma instance, you might also consider managing the user accounts via a separate LDAP database as explained in the official Akkoma documentation here. Please refer to our dedicated LDAP tutorial for the XMPP server part.
We are still looking into the best options to directly link Prosody to Akkoma or Pleroma. You might be able to use the same Oauth2 method as explained in the Mastodon integration tutorial or via a http basic auth module as explained in the Friendica tutorial.