https://twrp.me/sony/sonyxperiatx.html
The Xperia devices have a recovery-in-boot arrangement. This means that the recovery is booted using the regular kernel / boot image in the device. Team Win has worked with the FreeXperia device maintainers to come up with a way to extract the ramdisk from the FOTAKernel partition and use the ramdisk from that partition instead of the recovery that is included in the boot image of your device. This means that if you install current CM nightlies and flash TWRP to the FOTAKernel partition,