It doesn't matter what EU/world country the aeroplane is registered with. EASA has nothing to do with homebuilt or permit aeroplanes. There are no international agreements for permit aeroplanes. So, it is very difficult to move such aeroplanes to and from any national register.
If your mind is set on an RV then buy one which is already on the register of the country where you intend to operate it. You will find many dutch registered home built aeroplanes on the market but you will have the same issues trying to register it to another country. There are a number of dutch registered home built types here in France. Some of the dutch sellers have agreed to keep the aeroplane, in their name and address in the Netherlands, so as to retain it on the dutch register. Its a very unreliable risk: the dutch seller may change their mind later or sadly die. None of the EU countries allow you to keep a home built aeroplane permanently in the country without it being registered.
The RVs are fabulous aeroplanes. As others have said a good example of an RV at the right price sells in days. The key then is to buy wisely.