LiveKit, the "open stack" they rely on ties into VC-funded US tech used for border surveillance https://livekit.io/customers
Second, why do you use scare quotes on "open stack" when the entire stack does indeed appear to be open source?[1] If Visio is in some capacity using LiveKit, it seems not just plausible but very likely they are building their own infra using LiveKit's stack rather than paying LiveKit for SaaS.
Third, under the reasonable presumption that any use of LiveKit would be using LiveKit's stack on their own infra, why would it matter who else uses LiveKit?
In short: I try to assume the best, but it seems very much like your post is a shallow attempt at muckraking.
[0]: https://cyberinsider.com/france-to-replace-zoom-and-teams-wi...
[1]: https://github.com/livekit/livekit as noted in other comments