@toughcaddy No matter how unhappy I am with possible problems in the current release candidate, I am planning on forgoing all updates for at least 1 year.

@toughcaddy Just wanted to give Oneplus 6 users a heads up that the latest stable version of UT, OTA-22, has the same problem with the bootloader warning. OTA-21 was free of this problem. Unfortunately, OTA-22 even fails to boot the very first time after installation via the "Updates" option in system settings within Ubuntu Touch. I was able to get past the bootloader warning (i.e. boot into UT) only after I installed the latest release candidate via UBPorts Installer, as described in my previous message. One has to select the RC channel in the UBPorts Installer during the installation.

@magdesign You're a lifesaver!! Using my Ubuntu notebook and UBPorts Installer, I was able to install the latest stable OS, 16.04 OTA-21, without losing any of my previous data. It doesn't get stuck in the bootloader warning.

@magdesign Thanks, the Release Candidates worked fine for a while, but the latest small update (February 12 or 13, I think Ubuntu Touch 45, size 6 MB) resurrected this problem, I haven't been able to boot my phone into Ubuntu Touch for 2 days now. I have tried what worked before a hundred times, nothing works.

@toughcaddy I found a better solution than pressing the power button alone several times. First, enter the "Recovery mode" (not "Reboot to recovery"!) by holding the volume up and power button. When you reach the fast boot mode choose "Recovery mode" by pressing the volume up and down buttons and make your selection by pressing the power button. When in the Recover mode, select Advanced and then Power off. After that, try using the power button alone. If you still get stuck in the bootloader warning more than once, then repeat the Recovery mode procedure. With this approach, I never have to turn off and on my OnePlus 6 more than two times before it loads Ubuntu successfully.

@toughcaddy P.S. This bootloader warning seems to get stuck when you choose the "reboot" option within Ubuntu on Oneplus 6. My advice is to always choose the "shut down" option in Ubuntu instead of "reboot" and then to use the power button to turn the phone back on. If the warning gets stuck, then use the power button alone several times as described above.

@digital_wookiee My Oneplus 6 has the same problem after I installed Ubuntu Touch. What works for me is I simply use the power button alone several times. To be precise, when the "Bootloader is unlocked" warning persists for more than 2 minutes, I hold the power button to turn off the phone, and then hold the power button again to switch the phone on. Two or three times usually does the trick, namely, the bootloader warning stays for only several seconds, after which Ubuntu loads successfully.