I have seen other forums discussing "bulb failure" warning with LED lights on trailers. This is not exclusive to Yetis, the situation is mentioned in regard to Tiguans and Ford Rangers.
Hopefully this is useful info for anyone looking at ordering a Yeti with a towbar, remember of course that we are in Australia.
We purchased our Yeti and had the towbar fitted by the Skoda dealer in Coffs Harbour.

It is a Best Bars unit, from NZ. A conservative load limit of 600kgs unbraked & 1200kgs braked, that suits us because the heaviest thing we would ever want to tow is a rental campertrailer. It is detachable, the kit included the 11 pin round to 7 pin flat adaptor you see above. When a trailer is attached the trailer warning image appears on the parking screen and the beeping is cut out. That is my homemade trailerboard for bikeracks etc.you see in the above photo.

When I attached the boat trailer for the first time the "bulb failure" symbol appeared. The local Skoda service department (run by a lady!) said it was the LED lights on the trailer, to rectify it I should install incandescent lights on the trailer. So I did and everything works great.
If you wish to have LED lights, an auto electrician said it is a simple job to fit a resistor at the electrical coupling and this will fix it too.
The trailer board for the bike rack which you can see on the first picture uses normal lights as well.
I was pulling away from the boat ramp the other day and the warning symbol appeared. On inspection is wasn't the bulb but the 7pin plug on the boat trailer (which is over 10 years old) needed a little TLC, 5 mins with the philips head and we were underway and legal.
Safe travels all, Rob.