Awesome
beeper-imessage
A Matrix-iMessage puppeting bridge.
Documentation
The bridge works like any other mautrix-go bridge, so the instructions at https://docs.mau.fi/bridges/go/setup.html can be applied directly. You can find precompiled binaries from the GitLab CI at https://mau.dev/mautrix/imessagego.
Additionally, the bridge requires a registration provider running on a Mac or jailbroken iPhone, as well as a relay server to help the bridge and registration provider connect to each other.
When connecting the bridge to your Beeper account with bbctl, you don't need to self-host the relay, you only need to run the provider.
Discussion
Matrix room: #imessage:maunium.net