Separate Websites mit FluentSupport & BetterDocs. Für Auto-Login, siehe
Auto Login to WordPress from another Website – Carlo Fontanos
https://carlofontanos.com/auto-login-to-wordpress-from-another-website/
WP Login and Register using JWT – WordPress plugin | WordPress.org
https://wordpress.org/plugins/login-register-using-jwt/
How to Single Sign-On to Multiple WordPress Sites
https://zeropointdevelopment.com/how-to-single-sign-on-to-multiple-wordpress-sites/