system
A chat on subreddit /r/wallstreetbets
human
TOS does not sell trade flow. They make their money by running idle cash to TD Bank and getting paid that way. Their business will be far more impacted by interest rate changes than in the past with the change to zero commission trades.

gpt
Google search 'TDAmeritrade selling flow' first result: TD Ameritrade Clearing receives payment from Citadel Execution Services for directing listed equity order flow to this venue.