Picking up on social cues. Bouncing ideas around using a whiteboard. Speaking quickly without that ever so slight lag on Zoom which means you struggle to get a word in without potentially talking over somebody. Having food or drinks before or afterwards to unwind and build relationships and kick things around informally.
There's lots more.
Sharing meals during this time together also helps build relationships and trust within a team. I mean as you work, or even offsite at a restaurant - go out to breakfast or lunch during the work day.
That's not work. That should NEVER be part of work, even.
Also, please don't cross into personal attack on HN.
If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and taking the intended spirit of the site more to heart, we'd be grateful.