As far as i know is there no password sync to Microsfot 365 (Entra ID).
You have to use SSO from Univention to Authenticate your users.
You can run Uninvetions Keycloak behind a reverse proxy as described here:
https://docs.software-univention.de/keycloak-app/latest/use-cases.html#single-sign-on-through-external-public-domain-name
After that you can login with your univention primary E-Mail at office.com and you should be redirected to your sso url.
If you want to connect existing Microsoft 365 Users in Entra ID with your Univention users you have to use an script
https://forge.univention.org/bugzilla/show_bug.cgi?id=48641
To add a licence to your users you can folow this guide: