Dear members and visitors, I have the same problem with steveblue and after I read all of your posts I finally concluded. I just wrote a friendly table, so everyone can read and understand it, with real examples. I can't cover all combinations but those I have tried is enough to understand your needs for your case and to apply them for the best solution:
Apple Computers Memory Cards Compatibility
Card Reader (internal or external) new + OS new
Card Reader (internal or external) old + OS new
Card Reader (internal or external) new + OS old
Card Reader (internal or external) old + OS old
SD card old
OK
OK
OK
OK
SD card new
OK
FAIL
OK
OK
SD card old is like 32 GB (FAT32) simple or less (<=2015)
SD card mid (old / new) is like 64 GB simple / 64 GB Pro&stuff (2015-2016)
SD card new is like 128 GB (ExFAT) Lexar 1000x Pro or better (>=2016)
Card Reader External old is like USB 2.0 (<=2015)
Card Reader Internal old is like iMac late 2013 or older
Card Reader External new is like USB 3.0 and newer or USB 2.0 but new chipset/generation (>=2016)
Card Reader Internal new is like Mac Book Pro Mid 2015 or newer
OS old is like El Capitan, maybe Sierra/High Sierra and older
OS new is like Majoave, Catalina, Big Sur and newer.
Mihai Ditiu got a reaction from George_P in Anyone having issues reading card media in MacOS 10.15 Catalina?