I heard about Betfair leaving Netherlands and I always sympathize with situations like that because that's often one of those doomsday scenarios for aspiring traders, although you don't seem to be too heartbroken about it
In short the only legit way is to ask Betfair to change the country/address on your account, for which you obviously need sufficient legit proof, but then wherever you want to reside you can trade via VPS like Bet Angel and others.
For specific advice it's best to ask around on digital nomad communities like Reddit, long term for the more serious "foreign" Betfair participants it's probably not a bad idea to invest and get your name on a piece of property somewhere in places like the UK or Malta etc.