I tried to read some external memories with my device, but I discovered that any of them were detected / read.
It seemed strange to me, since I used the same method when I installed /e/OS on the device … and I used exactly the same equipment (a cable USB C to USB A, a memory stick).
Therefore, I tried another cable, memory stick, I even tested SD cards with a different adapter, but nothing changed …
I checked the settings, and found “Developer options > Select USB Configuration”. I changed from “Charging” to “MTP (Media Transfer Protocol)”, rebooted, but nothing … it seems that the device does not detect anything connected to the USB port …
My Sony will only read my USB drive if the connector is inserted a certain way (seam side facing the same direction as the screen). You might try turning the connector 180 degrees and see if it is read that way.
Just some feedback after trials (with different USB C to A adapters, memory sticks and SD cards).
Everything worked fine, without needed to adjust any settings. I could read the memory sticks and the SD cards.
Just a comment fro @Taurus : I tested the USB C connexion both sides, and in both ways I could read the memory sticks / SD cards (which is nice, although it was not so obvious, after thinking about your comment). So I do not understand what was wrong when I did the test some days ago …
By the way, I noticed the following: although ejecting the USB device before physically removing it, sometimes the device froze / rebooted … my conclusion is that it is not a good idea to repeatedly remove / swap USB memory sticks / turn the adapters upside down and so on … it seems the device does not appreciate it . It should not be a big issue, since the real usage would be connecting only a memory stick, manage some files, and finaly eject it.
I will mark the thread as [Solved], since it seems now OK (although it is still not clear to me why it did not work few days ago … )
The metal USB-C connector end that inserts into the device has a faintly visible seam on one of the long sides. For my phone, I have to insert the connector with that seam facing the same direction as the phone’s screen, otherwise it won’t be available for file transfer. If I insert it with the seam facing the back of the phone, it doesn’t mount correctly. Could just be a quirk of my USB drive.
I haven’t experienced any of the problems you mentioned regarding safely removing/ejecting the USB drive.
I understand, that’s why I tested (because, when I had used it to install /e/OS, I had experience no issue, and it is seems unlikely that I was so lucky to plug it the right way every time ). And it is a reason why I consider strange (and fortunate) that it works both sides, since USB C is symmetrical (and they made it smart enough to work in both ways), but on the other end, I have a USB A connector, which is not symmetrical at all … my conclusion (disclaimer: I know nothing about hardware ) is that USB C was developed in a very smart way
Now, everything seems ok, therefore, thank you again for your replies.
. It should not be a big issue, since the real usage would be connecting only a memory stick, manage some files, and finaly eject it.
). And it is a reason why I consider strange (and fortunate) that it works both sides, since USB C is symmetrical (and they made it smart enough to work in both ways), but on the other end, I have a USB A connector, which is not symmetrical at all … my conclusion (disclaimer: I know nothing about hardware 
) is that USB C was developed in a very smart way