Already used another tax filing system that is free and the return was accepted.
No. Just leave and abandon it. You can try to clear it. If you haven't filed, registered or paid you can try to clear
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-clear-and-start-over-in-turbotax-online/00/26444
There is no need to tell TurboTax that you filed elsewhere. TurboTax is not going to do anything with your information. If you get an email from TurboTax saying that you haven't filed, just ignore it.