I think most of them use delayed quotes of Papertrading. This is because real-time data is expensive
I use TradeHawk for my papertrading and live trading
I know you can do it. Before I moved to TradeHawk I used to do it with TWS. Individual account holders have the ability to add multiple users to their same IBKR account
I saw this question. Looks like they are honoring existing Tradier accounts too,
Also I am a new user. I got it too. I went to https://brokerage.tradier.com/platforms/esignal clicked on promotion and request and they reached me back.