Solved with the help of Dell customer service  
I live in Poland and I've bought a monitor U3421WE from the German Amazon directly (Sold by Amazon). I'm unable to use product detection so I am trying to use ownership transfer, as the Dell support page suggests. I'm filling previous owner (Amazon EU S.à r.l., Niederlassung Deutschland) data properly, but when I try to fill in the new owner information Dell's page just keeps asking me to select one of the German 'state/province/county' for a Poland which makes totally no sense. Also, that field is required so I'm unable to move to the next step of the form and finish my ownership transfer. I'm worried that buying not a cheap product for its 'trusted support' will end up with having 'just' a product... What am I supposed to do to be able to fill in new owner data properly?Regards,Marcin
International ownership transfer