I'm pretty sure it's as simple as setting up SCEPman following their decent documentation. After that, you can simply enable the 'RADIUS local auth' option, choose certificate based authentication, tick a couple more boxes and then upload SCEPman's Root CA certificate in PEM format.
Then configure your endpoints to connect to that wifi network using certificate-based authentication.
@GIdenJoe 's setup is more comprehensive as it also uses a cloud-based RADIUS service that you could use for a load of other stuff but what I've suggested is very simple and apparently works well for simple and secure wifi access. I will be looking to implement something similar before long, so I can retire our internal NPS server.