How to change campaign setting from hybrid to virtual?

You can change the campaign setting details in Campaign Settings of the admin site.

Go to Org's Admin Site > Design Event Campaign (for your campaign) > Settings > Go to Hybrid/Virtual Event section > select your choice of event type as below:

Choose Hybrid Event if you want to sell both in-person and virtual tickets.
Choose Virtual Event if you want to stream using 3rd party like Zoom.
Choose Tikkl Stream if you want to use Tikkl Live Stream to stream your events (with Live+Replay, only Live, and On-Demand streaming options).
For In Person events, keep all checkboxes unselected (by default).