The A321’s are not the new NEO (New Engine Option) version, but instead, the CEO (Current Engine Option).
Freighter aircraft fly far fewer cycles and hours per day than a passenger carrier. There are many, many markets for these aircraft. FedEx has nearly 100 757 converted freighters that were all converted after airlines retired them, some with close to 90,000 hours when converted. There are still DC10, converted MD11’s, converted A300, converted B767 and more flying for all kinds of cargo airlines.
The story actually misses the mark slightly. The conversion STCs are owned by large maintenance facilities which convert and sell the aircraft. Yes, smaller regional freight carriers will buy some of these converted planes, they always have, but the big market will always be the large fleets.
Airbus and Boeing often support and assist with these conversions, as it provides a second hand market to passenger carriers, who are then free to purchase new airframes.
As far as recession fears, freight moves in the airline industry even in down times. Unlike passenger carriers, freight and overnight carriers rarely, if ever furlough pilots. UPS has had one very small furlough and FedEx has never furloughed. During 2020, when passenger carriers were parking airplanes, laying people off and offering early retirements, the freight airlines were increasing routes and hiring as fast as they could.