Can I still subscribe to a trader even if I don’t have any Binance Spot portfolio to auto-copy?

Yes, it is still possible for you to subscribe to a trader without a Binance Spot portfolio but note that you will not be able to auto-copy the trades made by the trader. Instead, you will be required to enter the trade manually. For auto-copy trading to work, you must have a Binance Spot portfolio. Do note that FTX and FTX US are no longer available.