Which OpenTx Revision For Ghost

There are three revisions of OpenTx which are suitable for use with Ghost: 

1. Standard Revision (pre-2.3.10)
For users who do not wish to upgrade their version of OpenTx, there is one path to using Ghost, with the SBus Protocol. Simply set the OpenTx external module protocol to SBus, and the Ghost Tx module should automatically switch to it. 

2. IRC's Custom Build 
The OpenTx binaries available in the 'Firmware' section of IRC's Ghost Product page should support most, if not all, OpenTx radios, and contains an OpenTx build with the 'Mixer Sync' (OpenTx->Ghost) synchronization, with the best performance possible, in GHST protocol mode. 
This is the build recommended for race pilots. 

3. OpenTx Official Build 2.3.10
This is the first official public build of OpenTx which supports the GHST protocol, but does not yet support the 'Mixer Sync'. 
It is recommended for pilots who want to 'play it safe' with an official build, and are not concerned about having the absolute best performance. 

Note that to determine the correct OpenTx Binary for your particular radio, please use the OpenTx website, and other resources. ImmersionRC are not experts in providing this information. 
https://www.open-tx.org/downloads