There’s no built in function for event registration more than the meeting function! You can create a channel meeting which will give the possibility for all team members to join! If you make sure they subscribe to the group calendar they will receive an mail too! Other methods I’ve used is to create a invitation form using forms where you can also collect information from attendees! The link to this can be in the meeting so all the people get it or sent separately! Just a few tips...
Thanks so much for the replies and sorry for not getting back to you earlier. I've tried a few things out but I am far from satisfied.
Therefore I've changed the direction of my search to a good external meeting app / software that can then be integrated into teams, outlook etc. It seems to be the most pragmatic way to proceed from here.
What's the minimum level of access to a Channel that is required to subscribe All Team members for an alert (if something is 'urgent' or 'required') and alerts/notifications have not been subscribed to by all users? Understanding subscribing for alerts is configurable per user; however, if you want 'items' created by 'user x' to generate notifications whether Team members are subscribed or not.