Thank you guys! Quick question, if I'm on T-Mobile 10.5.10 (unlocked, can't receive OTA updates), do I need to flash 10.5.7 and then upgrade or can I just flash 10.5.21 straight away?
Once you use this tool you will be at the latest software so there will be no ota update to update to.
Otherwise, if you used an older cersion file to flash, you will have to take the ota update before you can even flash twrp much less root cause Tmobile are nazis