The site Event Marketer (https://www.eventmarketer.com/) has created an amazing list of "THE 2021 VIRTUAL PLATFORMS INDEX"
The site mentions and we quote it as follows - "To make the job easier for event marketers in search of just the right platform for their portfolio of 2021 events, we created the Virtual Platforms Index. Each profile includes vital information on the industry’s top platform providers, all designed to help you get to know who’s who, who does what, and quickly compare features, review case studies, client rosters and pricing, and narrow down your choices to just those providers worth a closer look."
You can have a look at the original article on their website here