There has been a previous discussion on this topic:
That led to the suggestion to set up and trial a free software alternative to ensure that it can offer a solution that works reliably. We have people from around the world joining for sometimes reasonably large calls (20+) and Zoom provides a good experience for participants, including those joining from phones in places with limited bandwidth.
There has been a group meeting periodically to look into this and other free software tools for the GOSH Community:
To date, we don’t have a tried and tested free software alternative to Zoom that we’re confident will work as seamlessly. Some GOSH community calls therefore use Zoom, particularly the public-facing ones. Providing opportunities for people to talk to each about open science hardware feels more important than the platform that communication happens on.
The group looking at new apps for GOSH would I’m sure welcome new members willing to help set up and test other options.