@cristodcgomez sorry I was unclear: I have also tried selecting "restart" from the bootloader screen as per your hint above, and that also didn't result in the phone being recognized by ADB.

My extra attempt was to go through the recovery menu, which just locks the device when I select the fastboot option.

At this point I feel like something went wrong in the UT install that has messed up my phone's ability to access fastboot.

@cristodcgomez you gave me hope, and I tried...but this isn't working either

I can get it into this screen (no ADB/fastboot recognition):

Then I can reboot into "recovery mode"

As soon as I attempt "Enter Fastboot" option here, the phone locks and I have to long-press the power button to restart:

In none of these screens is the phone recognized via ADB. When UT is loaded up, the device is recognized, but I can't send it commands such as to reboot.

This is what I'm seeing when attempting to flash the original FP4 OS using Fairphone's utility while in the bootloader, with "FastBoot Mode" in red letters and "DEVICE STATE - unlocked":

Again, the device is in Developer Mode within UT, and it shows up to ADB when UT has loaded, but ADB command to reboot is refused.

@Tafitson Thank you, this did get me into fastboot mode. I also found that Fairphone's method of holding "volume down" + plugging in USB works, too.

Now when I'm in fastboot mode, I can't get the computer to identify the device (tried on both Linux and Win10). It shows up just fine when UT is running and I use:

./adb devices

command in Win10.

But then if I try to use the command:

./adb reboot bootloader

Then I get the error "Failed to write reboot parameter file: Permission denied".

That combined with the lack of device detection in fastboot makes it seem like the "Enable Developer Mode" option isn't correctly enabling ADB on the device or something? I don't know, I'm at a loss.

So I installed and tested UT on my FP4, and it just isn't quite for me yet. I was going to re-install the FP4 ROM as per Fairphone's instructions, however I can't get into fastboot mode from the bootloader.

I use "volume up + power" key to get into UBports Recovery menu, then select Advanced > 'Enter fastboot'. But from there, the device just becomes unresponsive, and it isn't recognized by the Fairfphone flashing utility (using Windows). If I hold power button I get an active black screen, and device remains unrecognized by flashing utility.

(Selecting "enable ADB" from the same menu gets me to a black screen with "ADB enabled", but again the flashing utility doesn't recognize the device.)

Using the SDK Platform Tools in Windows, the device is recognized when UT is booted up but when I attempt to run "adb reboot bootloader" I get the error "Failed to write reboot parameter file" Permission denied". Developer Mode is enabled in UT.

I'm at a loss here...any ideas on why I'm failing to get into fastboot?