Bakkt is a bitcoin futures exchange and digital assets platform founded in 2018 by the Intercontinental Exchange (ICE), the parent company of the New York Stock Exchange (NYSE).
The company initially planned to open its futures exchange in 20181, but postponed its launch due to the volume of interest and the work required to prepare its services2. The launch of the futures exchange was subsequently delayed several times after due to regulatory issues, reportedly pertaining to asset custody3. Bakkt began testing its platform in July 2019 while waiting for regulatory approval to take the platform live4.

BAKKT Will Launch September 23, 2019, 8:00 pm - America, New York

So where to trade Bitcoin on that date? I would go for leverage places for most.

But on spot.. mostly anonymous bitcoin exchanges where you have many. Here are a few to check:

Binance - the obvious top vol exchange, has STEEM
KuCoin - i would call it younger brother of Binance with many NEO and ETH pairs
BiBox - amazing China exchange, similar to other two above with different coins
BitMax - free transaction mining and fees share of what exchange makes with BTMX tokens
CoinExchange - many ETH tokens and anon coins like ZEC XZC EXCL
Coinex - ETH BCH BTC EOS pairs
CryptoBridge - decentralized exchange build on BTS, the older brother of STEEM