Web Whiteboard
Web Whiteboard is a free (for 21 days), online utility that allows participants in an online meeting (Google Meet, for instance) to have access to a whiteboard where collaboration can take place. Students do not sign in to the service, so it is safe for use in K-12 classes. This may be a valuable tool for online delivery of lessons.
Once the free trial period has ended, the cost to continue is $8 per month.