We, Surekha Technologies, recently published a Video Conferencing App for Odoo V13, V14 Community Edition.

This is a secure and manageable application to organize frequent meetings with the customers or colleagues. It provides secured user authentication to join any meeting from Odoo or a self-hosted server.

Features are:

• Secured authentication and authorization for members to attend video calls/conferences through private or public meetings.

• Can manage and schedule the meetings efficiently.

• Any number of members can join video calls/conferences.
  
  

Check out Odoo Video Conferencing / Call App: 
For v13: https://apps.odoo.com/apps/modules/13.0/st_video_conferencing/
For v14: https://apps.odoo.com/apps/modules/14.0/st_video_conferencing/

you can try this module https://www.odoo.com/apps/modules/12.0/voip_jitsi/

I´m in search of that too - maybe CometChat (https://www.cometchat.com/) has the possibility to become integrated?

In CometChat you can create chat-rooms for video-chat and invite users to join.

Additional you have the possibility in broadcast something and invite users to watch (comes close to webinar-functinality...).