As important as drawing the casus belli is laying out alternatives. What are the alternatives to Zoom, supporting Linux, OSX, mobile and Windows, with decent terms of use?
The page suggests using Jitsi instead (https://meet.jit.si/), which is apparently open source and can be self-hosted. I've never used it, just pointing at what the page suggests.
It's easy enough to host as a small set of containers behind a reverse proxy. Bandwidth is the main bottleneck in my experience, but there is peer to peer to some degree.
Used it loads, it's great.
Jitsi is amazing. I tried out the desktop client version maybe 10 years ago and it sucked hard. More recently, using their webRTC version has been the smoothest voip experience I've ever had, and it's gratis, and it's open source, and I don't even need to register. It has high quality audio, video, and screen sharing. Honestly, I have no reason to use anything else.
The article suggests jitsi and I have had success using it in all the platforms you mentioned.
We use Whereby for quite a while, and it works very well. It runs in the browser and does not require any installation (I think they are based on Jitsi).