Sources: secretive options-trading giant Susquehanna International has a 15% stake in ByteDance, estimated at $15B+, making it the largest outside investor (Wall Street Journal)

Wall Street Journal:
Sources: secretive options-trading giant Susquehanna International has a 15% stake in ByteDance, estimated at $15B+, making it the largest outside investor  —  Susquehanna International Group is sitting on stake in app's owner estimated at more than $15 billion