No new Intiface client installation is required. Buttplug, which is included in the game, will attempt to connect.
My device is a custom configuration, it’s not included in the hardcoded list of devices of the Rust FFI library you are using. I contacted buttplug.io support and they told me it’s not possible to connect. I can only use it via Intiface. So unfortunately it will not be compatible and the game will never see it (I tested).
Is it too difficult to make the game use Intiface on a future update?