Last year I received a 20k loan with no interest from a personal US bank account that belongs to a non resident, non-us citizen. How do I report this on Turbotax?

You do not need to report a loan on your tax return, as it is not considered income.

If you receive a gift in excess of $100,000 from a non-U.S. citizen you must file a report and a no-interest loan could possibly be perceived as a gift. However, you are still under this reporting threshold.