@lduboeuf Also, in case I wasn't clear about this, the USB data transer was working with Ubuntu Touch for a long time and then stopped.

@MrT10001 I have a passcode (although I also have a fingerprint set up if that matters). Developer options are on. I have restarted the phone. On one of computers has adb 1.0.39 and the other has 1.0.41, and neither of them are able to see the phone while it's unlocked and plugged in (either with adb devices or in the normal file system). I'm still looking but I haven't been able to figure out how to check the fastboot driver version yet (or what the most recent version of adb is for that matter).

@etdoughe It is version 16.04 and OTA-25.

@Ian The folder does not appear. The computer does not even visibly register that a USB device has been attached (although the phone does start charging). I do have adb. When I run adb devices with the device plugged in and unlocked, it does not list anything. Using the same cable with my Pixel 6a (running Android) adb devices does list it when I enable USB debugging.

I have Ubuntu Touch installed on a Pixel 3a. Recently I have been unable to transfer files over USB. I have tried several different USB cables and several different computers (with both Linux and Windows), and I have made sure to attempt this with the phone unlocked. The device is able to charge via USB. Furthermore, I am able to use a USB keyboard with the phone.

Obviously this might be a hardware issue with the phone, although in my experience usually a failing USB port will work intermittently and this has just stopped completely. How can I determine whether this is a hardware issue, and what other steps could I take to fix this?