I really appreciate all the thoughtful responses to the original question of what to do with an EIP to a person who died in 2019.  Here's my takeaway:

1. This isn't a tax/IRS issue, it's more analogous to an erroneous Social Security payment.

2. Social Security recoups erroneous direct deposits by backcharging the account. So I'd leave the cash in the account for now and see what, if anything, happens. My guess is nothing happens. 6 months from now, distribute the money to the heirs.

3. Erroneous physical checks are a different animal. Chase Bank has taken the formal position, which I think is correct, that they won't cash a check that says "Dec'd" on it, which is my situation. So I'm going to frame the check along with the eventual letter from Trump, a 5 cent refund check from my HMO, the followup letter from my HMO asking why I hadn't cashed the 5 cent check, and a $9 securities fraud class action settlement issued in 2019 to my dad who died in 2007.