I have come to the conclusion that this is the way forwardI've nearly always done all my own servicing of cars, vans and bikes inc the first 500 mile and had warranty work done. If I messed it up I know the warranty wouldn't cover it but if they refused genuine warranty work I would tell them I would never buy a car bike van from that manufacturer again and for them to make a commercial choice.
In this instance, you're in a stronger position because you have your bike booked in, dealer has closed with no notice and you need the service done before you go away. I'm assuming it's not a valve check and only needs oil and filter + checkover? I'd have it done quicker than riding to the dealer.
Use the correct grade of oil and a genuine KTM filter, take pictures if it is a valve check and keep the receipts.
You'll be fine and it's quite satisfying knowing you've done it.
As far as I can see for the warranty to remain valid it has to be serviced in accordance with KTM schedule using KTM genuine parts by a competent person ( I.E not me
)So it snow and in the future going to be cared for by the extremely good lads at Doncaster Motorcycles ( blatant plug https://www.doncastermotorcycles.co.uk/ )
Neil and Kev are both very diligent and extremely competent