I also DM that same link when I’m promoting registrants. I had to include steps like step 1 open the message step 2 click the green register button 3 add to your calendar, but I agree would be nice to have a link that you can Dm that allows them to click register direct in the Dm without all the steps.
For sharing it into other channels, you could start with one channel for the first post. Then go in and edit the event and add another channel. It will then add a new message to that channel with the event.
Maybe that will work as a work around for you, Mary G.?