Installer stuck at "Asserting unlocked bootloader variable ..."

[nogoogle]

I am trying to install UT on a new FP4 using UB-Installer 0.97 beta.

I followed all instructions on the FP website to unlock the bootloader and I verified that Android 11 is installed, USB debugging enabled.

When I connect the phone (turned on, Android booted) to the laptop, the phone is recognized by the file manager and the installer. I choose the install option (including wipe) and the installer reboots the phone into fastboot mode but it then is stuck at "Asserting unlocked bootloader variable".
The fastboot screen says "DEVICE STATE - unlocked" but does not list a bootloader version or baseband version. SECURE BOOT is set to yes.
However, adb devices in terminal does not list any device.

When I reboot to Android, adb devices lists the device.

Is there a step in the process that I missed? Any suggestions?

Thanks in advance for your help.

[wynn1212]

Which platform are you using UBPorts Installer?
If it's on Linux, try with USB2.0 port or USB 2.0 cable.
Or try UBPorts Installer on Windows.

For me, I have the same problem

stuck at "Asserting unlocked bootloader variable".

when reflashing Ubuntu Touch on my FP4 via UBPorts Installer on Ubuntu 20.04/22.04. But I'm pretty sure it used to be working when I flashing Ubuntu Touch first time. They must to be the update (maybe kernel, android-tools or fwupd describe here: https://unix.stackexchange.com/questions/684494/fastboot-recognizes-device-but-unable-to-flash-stuck-with-no-output-on-ubuntu/747584#747584) breaks it. After pinpoint down the problem, it seems to be stuck at fastboot command. Since I have already tries different cable, usb ports, etc...

My solution? by using windows 10/11 to flash Ubuntu Touch via UBPorts Installer. After install the driver, it works out of the box.

[nogoogle]

@wynn1212 Thank you for your detailed reply. I was using Ubuntu 24.04.2 with Kernel Linux 6.8.0-57-generic both on and old AMD desktop first then on a Windows Surface Laptop (running same Ubuntu version) with a USB2.0 to USB C cable. Next I tried a USB C to USB C cable on a Dell laptop (also running latest Ubuntu version) and after 2 or so attempts the flash was successful (not clear why).
However today, I did the same procedure with another new FP4 using the Dell Laptop and USBCtoC cable and it again failed initially. When I connected the phone (already in fastboot mode) and restarted the bootloader from fastboot when installer was asking to manually switch the phone to fastboot, I was successful.
This is quite frustrating because it still is not clear to me how to exactly reproduce this issue. It is definitely not the cable or the computer used. I agree this must be an interaction between the Ubuntu version and/or kernel and the phone. It almost looks like a timing issue, restarting bootloader at the right time lets the process go through.
I could not test on Windows because I only have a work laptop running windows which does not allow starting non-certified appimages.