I've seen articles online suggesting that a W-2c will be issued to the taxpayer.  I've NEVER seen it happen that way.  If you have a W-2c, just adjust the numbers accordingly on the W-2 Wks.

If, instead, it happens like itonewbie suggests in the "solution" to this thread (which is how I've seen it done EVERY time) what I do is enter a 1099-R in the current year for the deferral amount with Code P and there's a checkbox down the Wks a little ways, something like "1099-R received for 2021 with Code P."  That will add the amount to wages on the 1040.