I am going to take the web server database offline briefly later this evening to make a backup before trying an experiment with Nextcloud.  In the past I have gotten the external_authentication module to work for versions it was not designed simply by altering the definitions file associated with it.  I am going to see if I can get NextCloud HUB 4 to work this way.  By backing everything prior, I will have a way to return to NextCloud Hub 3 if it does not work.  I will do this after midnight so as not to interrupt much normal use.