Hey Punting - NDXT is a US based fund so essentially not eligible for trading in Europe. Most funds we can trade here will have “UCITS” in the name.
ETF Screener | justETF - this is a good starting place if you’re looking for funds. Lots of info and a decent search capability.
You can find a handy guide here to see what can and can’t be added to T212: Stocks & ETFs requests Help - Stocks & ETFs requests - Trading 212 Community