Oh, Im sorry, I missed RMD when you mentioned the 8915E.
For and RMD payback, use the Rollover section in the 1099R worksheet, you dont use the 8915E...thats for Covid distributions that you want to spread over 3 years.
Did they return the entire amount (adding their own funds for the w/h?) or only the net?
You still use the Rollover section, just be sure you only rollover exactly what was recontributed. The withholding will be considered a payment and potentially refunded on the return.
"will the tax on the required minimum distribution that was returned to the account show up on the form 5498"
No one "returns" the tax, once it is paid to Fed/State. It's just part of any prepayment, withholding or estimated payment for that tax year.
The only way you avoid that is the taxpayer makes up the difference in their redeposit. That's why you examine if the redeposit (rollover) of an RMD (which had to be made by the end of August) is Gross or Net. If Net, that amount is a partial taxable distribution.
"Level Up" is a gaming function, not a real life function.