I've been busy setting up the new set of geographies from the 2020 ACS and found that this year's set of ZCTAs is exactly the same as last year.32989 and they are all the same.
I know there have been a number of new zip codes created in the last couple of years, and a few have also been removed or merged with others.And the excellent GeoCorr app (thank you, Glenn!) shows 785 new zips for 2020 (though 471 are identified as PO boxes).
Any idea why the 2020 set of ZCTAs remains the same as last year? There are plenty of new metros and cities this year, why not zip codes?
See the ACS Geography Boundaries by Year, note 5: "The Census Bureau is planning on publishing the updated boundaries for this geographic summary level with the 2021 ACS release."
Ah-ha! That's the answer. Next year they will catch up.
Thanks so much, Jonathan!