I have a OnePlus 6T and the bootloader is fully unlocked. Using the UBports installer for Ubuntu Touch, somewhere along the line my phone was bricked. The install asks you to put the phone into recovery mode, but when I do that my phone gets stuck at the "The boot loader is unlocked and software integrity cannot be guaranteed..." screen, and won't progress any further. How can I flash a new OS without the ability to move beyond the fastboot screen?