If you were to build a platform to host virtual event conferences, How would you make it?

What technical stack is best to use when one is trying to build platforms that result in a Virtual Event Conference Platform. How are they made/achieved? What is making this work? What is the back-end and the front end

For references, I am using these websites: https://samaaro.com/

Other options: HexaFair Dreamcast VConfex Kestone