Don't take my word for it. Test it for yourself or call the IB trading desk and ask them what they support.
What kind of instruments do you want to trade? Is the exchange on which your instrument of interest trades open 24/7?
I trade high volume gappers premkt a bit, but all with manual limit orders, with fidelity. Works great but I wish I could use OTO automatic hard and trailing stops like I do in-market
For equities, you can only execute using limit order during premarket or after hour. Thus that the reason why you can’t use a stop loss order premarket or after hour.
Thanks for all the answers guys, so I realize there is no way to protect a huge gap without sitting at the screen during after and pre hours.