Zitadel looks interesting, but their website is quite confusing. I'm not sure is it open source and free to use (as keycloak) or you need a commercial license to use "open source".
The software is open source under Apache 2.0 (https://github.com/zitadel/zitadel). No open core or similar, we run the same version on our Cloud Service and for Enterprises. Thanks for the feedback, we need to make that more obvious then.