I know this has been covered in some ways, but the solutions I could find haven't been working for me.
1. I am on Linux, no Windows, so I cannot run Kindle Fire Utility.
2. I installed TWRP and firefirefire with the following manual commands:
3. All the above seemed to go fine.
4. When I reboot and leave the power button alone, yellow firefire passes and I boot into the installed stock OS, no problem.
5. When booting and I press the power button until it turns orange, it gets stuck at the yellow triangle forever.
6. Powering off and rebooting does still work, so I'm not stuck in the loop (which seems easy enough to fix) but I cannot get into TWRP.
7. Many have reported this problem, and fixed it with Kindle Fire Utility. Since I can't use that, I'd appreciate it if anyone knows of a more manual fix.