My son, whom i claim as a college student, received unemployment compensation. He received a 1099-G. How do we file this?

"If his unemployment income reported on form 1099-G is less than $12,400, he is not required to file a tax return."

That statement is not correct.  Although the "normal" filing requirement is $12,400, special rules apply for dependents.  Unemployment compensation is unearned income.

You do not report his/her income on your return. If it has to be reported, at all, it goes on his own return.  Your dependent child must file a tax return for 2020 if he had any of the following:

1.          Total income (wages, salaries, taxable scholarship etc.) of more than $12,400 (2020).
2.          Unearned income (interest, dividends, capital gains, unemployment) of more than $1100.
3.          Unearned income over $350 and gross income of more than $1100
4.          Household employee income (e.g. baby sitting, lawn mowing) over $2100 ($12,400 if under age 18)
5.          Other self employment income over $432, including money on a form 1099-NEC

Even if he had less, he is allowed to file if he needs to get back income tax withholding. He cannot get back social security or Medicare tax withholding.

In TurboTax, he indicates that somebody else can claim him as a dependent, at the personal information section.