This link contains downloads for the latest Ethos version, as well as a download for the Ethos Suite for your computer which contains a transmitter simulator. You can select the transmitter you're interested in when starting Ethos Suite and try the Ethos environment out to see if you like it.https://github.com/FrSkyRC/ETHOS-Feedback-Community/releases

This RCGroups link contains much information on everything about the FrSky Tandem transmitters and the Ethos operating system. Check out post #2 for a large amount of links to different pieces of information about specific topics.https://www.rcgroups.com/forums/showthread.php?3703807-FrSky-X20-%28S-HD%29-X20R-%28RS%29-X20-Pro-%28AW%29-Tandem-24-Channels-with-ETHOS

https://rc-soar.com/ethos