HubSpot on any paid plan; Salesforce, NetSuite, and Dynamics 365 on Corporate. Which one to pick if you have more than one.
Four today:
We deliberately don't support two at the same time for a single organization. Connecting a second one automatically disconnects the first, with a confirmation before the swap.
If more than one CRM is a candidate, pick the one your customer-facing team uses day-to-day — that's where registration and attendance data will feel most alive. HubSpot for marketing-led shops, Salesforce for sales-led ones, NetSuite when finance owns the customer master, Dynamics 365 when it's stitched into the rest of your Microsoft stack.