Suggest to check the Xiaomi Mi Infrared Remote Control topic.
I actually prepared a regular json file for the device recently, but did not test it. I’ll try to upload it tonight for testing. In the mean time, would be good to see the debug log when you send the command to better understand what the device is responding. (as the mihome plugin uses very diferent commands involving the cloud). Please post in the remote topic.
Note you can connect the execute actions channel just the same in the 3.x versions. As before this channel is marked advanced, hence only visible when you check the ‘show advanced’ box