WordPress authentication with federated shibboleth and eppn

[Allan West]

My campus has lots of sites that use WordPress with shibboleth-based
protection of content, but none so far that were set up for federated
use with eduPersonPrincipalName (eppn) as the identifier of accounts.
Our web developers' templates aren't making WordPress happy with eppn,
in part because WordPress seems not to like the '@' symbol in what it
thinks of as user names.

Does anyone have advice on setting up WordPress to recognize eppn-based
user credentials in federation? I found things like the UIUC pages
    https://publish.illinois.edu/sbutler1/2014/07/16/wp-shibboleth/
on using eppn with local LDAP, but we're aiming to allow off-campus user
logins.

There are thousands of pages that proudly announce they are powered by
WordPress, so searching for other relevant terms and "WordPress" has a
maddeningly low signal-to-noise ratio.

Any references or pointers are appreciated!

Allan West
UFIT
allan at ufl.edu
352-273-1329