I would discourage any owner of a DSL-AC68U from updating to the newest firmware (Version 3.0.0.4.384_21126 (2018/07/05)). Chances are good it will brick your router.
See thread here: https://mybroadband.co.za/vb/showthread.php/963467-ASUS-DSL-AC68U-Firmware-Update-2018-07-05-Bug
See thread here: https://mybroadband.co.za/vb/showthread.php/963467-ASUS-DSL-AC68U-Firmware-Update-2018-07-05-Bug