Just in Case if you want to go back to stock, please follow the below to safely lock the bootloader and return to 100% Stock device:
Before you start, make sure you deactivate and uninstall all mods, magisk modules substratum overlays and any other system/build.prop mods that you may have executed/experimented with.
1. Download the latest full rom from my update thread
2. Move the Downloaded file from the Downloads folder to the root of device internal storage.
3. Navigate to Settings > System Update > Settings > Local upgrade > Select latest OOS Full Zip
4. Flash the Full Zip
5. Upon Successful Flash > Reboot to Recovery
6. Factory Reset and Wipe internal from Recovery to Reset the device
7. Reboot To Fastboot/Bootloader Menu
8. Connect the device and execute the below command
9. Select the Volume Button to Select Lock Bootloader and Power Button to Execute the command
10. Device will Reboot and Lock the Bootloader and there would be no more secure boot prompt on the reboot to confirm
Feel free to ask if you have any questions.
PS: Tested on Global Version, Please check T-Mobile thread for T-Mobile version, Thanks