I want users at my hackspace to be able to log in to WordPress from our existing SSO solution. I don’t want to have to pay the SSO tax. What are my options?

We're using MemberMatters to manage our membership and it acts as an OAuth2 provider, which we already use for Moodle, Grafana, and various other services.

I'm now looking at migrating from Hugo to WordPress so people don't need to learn how to use markdown and git to publish an update, but the only up to date plugins I see to implement SSO from a client perspective cost money that we just can't justify at the moment.

We'll be self-hosting to keep costs low as well, but I used to manage a shared hosting cluster with just over 500k wordpress/joomla/drupal installations so I'm well aware of the risks associated with self-hosting and have decided that this is the best option for our use-case.