I am new to this android rooting. I'd like to install custom ROM in an old Xperia SL. The bootloader had been unlocked successfully, and preferred next step is to install TWRP, then install custom ROM and supersu from TWRP.
The device has ro.secure=1 and no access to root. Does it need an insecure kernel to flash TWRP into recovery using fastboot? Or will flashing TWRP overwrite ro.secure and allow root access?