Just received the recall letter (Emission Recall 21E11) for my 2020 Explorer ST yesterday. I smell gas fumes in the car at various times and hear a tinny vibration sound when accelerating. I brought up the gas smell to the dealership in the past but of course they couldn't replicate it during the short drive around the block. I've got an appointment with the dealership for the recall next week. The service rep says it will be an "inspection" to determine if there's any need to "replace the left-hand catalytic converter". In my view, the replacement of the catalytic converter needs to happen regardless of what their inspection results are. I view it as a mandatory retrofit of a defective part and will make that opinion known to the service writer (in a casual way) when I bring the vehicle in.
Also, the information provided by the posters above is greatly appreciated. I'll give an update after my appointment next week.
UPDATE on 12/27/2022: brought the ST into the Dealership for the recall inspection, which took less than 30 minutes. They determined the part needs to be replaced and placed it on order (without prompting from me). The inspection took less than 30 minutes. Once the part arrives, installation will take a solid half day. Part expected to come in early next week, so roughly 7 calendar days.
FINAL UPDATE: the catalytic converter was replaced on 2/24/2023 with 39K miles on the odometer, the dealer also did safety recall notice 23S02/NHTSA recall 23V022 (a software download for rearview camera). All parts for the catalytic converter arrived within two weeks of the initial order, with the exception of the catalytic converter itself, which took close to two months to arrive. Both recalls were completed together in a single half-day. Very satisfied with the dealership, my Explorer ST and Ford in general.