Here's how to set up an ongoing virtual event, like a film to stream anytime, in Groundplan.
Add something like "Stream at Home" to the Title Prefix.
Add something like "Stream for Free" (if it's free) or "Watch" to the Buy button text.
When the streaming link is publicly available, add the link to stream the movie to the General Ticket URL. If they have to make a purchase, put the purchase link instead.
Option A - if the event has an end date
Set the first event instance to May 2 at the time the movie will be available online, and the last event instance to the last date the event will be available online. Set the performance type to Online Event.
Set the Event Calendar to No Calendar.
Hide the event from the general calendar.
Option B - If the event is ongoing.
Set the Display Date Override to say something like "Available on <date>"
Set the event to Unscheduled (below the Display Date Override).