The proper way to have them report your freelance income is on Form 1099-NEC. There is much confusion with the change from the 1099-MISC. There is no longer a box for non-employee compensation to be reported. Since your income is not Box 3 income, it has to be reported on Form 1099-NEC.
You can refer your customers to this IRS link: 1099-NEC
Form 1099-NEC.
The PATH Act, P.L. 114-113, Div. Q, sec. 201, accelerated the due date for filing Form 1099 that includes nonemployee compensation (NEC) from February 28 to January 31 and eliminated the automatic 30-day extension for forms that include NEC. Beginning with tax year 2020, use Form 1099-NEC to report nonemployee compensation.