I use a combo of the following (in order of reliability);
https://www.iposcoop.com/ipo-calendar/
https://www.marketwatch.com/tools/ipo-calendar
https://www.nasdaq.com/market-activity/ipos
There’s also https://www.renaissancecapital.com/, which probably gives more accurate info but isn’t free.
And in order for T212 to add the asset to the platform, the ticker needs to be loaded to Interactive Investor, which can be checked here: https://www.interactivebrokers.co.uk/en/search