Blueferry is an app that connects to your iPhone via Bluetooth to expose an iMessage bridge to your Linux desktop. It supports receiving and sending text-based messages, either 1:1 or in group threads. It requires no phone-side software or jailbreak - just Bluetooth pairing.

It accomplishes this by using an undocumented? behavior where enabling ANCS via Bluetooth LE (via https://github.com/pzmarzly/ancs4linux 's technique) causes the phone to accept message capability requests over standard Bluetooth. ancs4linux indicate that they've had mixed success with different BT chipsets on the Linux side, though all of the machines I've been able to test it on have been able to negotiate the connection.