I am trying to plug a 128Mb exFAT USB Drive into the USB-C port of the Galaxy S20 Ultra 5G phone and it doesn't seem to recognize it. A 64Gb exFAT drive seems to work fine. The 128Mb exFAT drive works fine when plugged into a PC or other device but not the phone. The phone shows a silent notification: "Charging connected device via USB". If I click on the message it shows "USB controlled by": Connected device and will not allow me to select "This device" from the option buttons. I tried another 128Mb drive and it had the same results. Is the drive too big?
You should be able to use up to 1 TB of Storage on a USB drive on your S20. But you might want to try Formatting the USB stick to FAT32.
Unfortunately, I can't format a FAT32 drive anymore because I am using Windows 10. Regardless, the suggestion doesn't make sense because it reads a 64Gb exFAT just fine. If it would recognize it as a USB drive I could format it on the phone, but it doesn't show up as a storage device.
I just tried the same 128Mb exFAT on a friend's Galaxy S20 (regular) phone and it works. For some reason it is not working on my S20 Ultra! However, other drives do work. Is my phone defective? Is there a difference between the Ultra and regular S20s?
Don't think that there's any difference as far as an external USB stick is concerned.
You can use the Samsung Members app Diagnostics to see if there's an issue with the Type C port on your device.
Open Samsung Members app & click on "help" & Start & then select the Type C port.
You can post the results here if you want.
Should be USB Type-C 3.2, USB On-The-Go
It's not something that you should need to update.
Here's the specs for your device from GSM Arena
DDid you try Formatting the USB stick to FAT32?