MULTI-Module firmware is not the same as the radio firmware, and must be updated separately.
MULTI-Module firmware updates are released regularly and updating the MULTI-Module firmware is quite straightforward.
The latest firmware can be found on the MULTI-Module Downloads site:
MULTI-Module Firmware Downloads
Checking the Version
The MULTI-Module firmware version can be checked by looking at the Module Status line in the Model Setup menu on the radio.
Module Status showing V220.127.116.11
After an OpenTX radio firmware update, the radio may tell you that there is newer MULTI-Module firmware available by flashing Module update recommended alternately with the version number in the Module Status.
Keeping your MULTI-Module firmware up to date is strongly recommended, as updates frequently add new features and address issues.
In order to update your MULTI-Module you will need to download the appropriate firmware file and use one of three available methods to write the file to the module.
Updating the MULTI-Module firmware will not affect receiver bindings - any receivers which are bound to the MULTI-Module will remain bound after the update.
Step 1: Download the appropriate firmware file for your MULTI-Module
In every release there are many different firmware files, each built for slightly different radio or module configurations. See the Firmware Files page if you need help knowing which file to download.