> It’s also worth noting that end-to-end encryption is necessarily broken as messages to (and from) WhatsApp, Signal and Telegram pass across the bridge(s). The bridge(s) operates in Element’s trusted EMS environment, with no content scanning or datamining, but currently bridged conversations are not stored end-to-end encrypted in Matrix (they will be in the future).

As a Signal user, I kind of don't want this to take off. I like knowing that when I message someone on Signal, it's for their eyes only. It feels like this service starts fragmenting some of the privacy guarantees of the bridged providers.

You can self-host. I suspect they use this: https://github.com/spantaleev/matrix-docker-ansible-deploy