I have been testing the Le Eco S3 with my Osmo Mobile for a few months now and can confirm this is fully compatible. Unfortunately, there is no 4k option on video recording.
Expected to update this dji go app?

Thanks for sharing your test result here, currently, 4K resolution is not available for all mobile devices and we will keep improving our product.
Temporarily, we suggest to use HID function, which means when you connect to Osmo Mobile's Bluetooth, you can also use the stock Camera APP in your phone to select 4k resolution for shooting, Osmo Mobile could just to a stabilizer. The shutter and video buttons in the handle can be used to control the volume button in your phone, thereby to trigger the video and picture taking.