Hello,
On the topic of online events, I noticed that the EuroPython Society had made some documents available describing their experiences with planning this year's conference:
https://www.europython-society.org/post/617463429296472064/sharing-our-resea...
Although they have chosen to use various proprietary services (hence the sharing of licences mentioned in the article), the online conference tools document seems quite extensive in its discussions of the tools and various experiences with them. It possibly complements the FSFE Wiki page on the topic of Free Software solutions.
Paul