Even though you had 3 years to repay the distribution, it was required to be reported as taxable income on your 2020 tax return. You would have the option of paying all the tax in 2020 or paying 1/3 each in 2020, 2021, and 2022. Did you do this?
If you paid the tax or have paid 2/3 and are paying the last 1/3 now, you don't need to do anything else. There is no need to report or disclose that you won't pay it back, you just pay the taxes. If you did not report the income and pay the taxes in 2020, you need to file an amended 2020 return to pay the tax.