USB Tethering Speeds - ASUS RT-AC66U

I have this on the latest official firmware USB tethered to a Samsung Galaxy A8 (2018). On 2.4ghz or a wired connection the maximum download rate I can get is around 30mbps. On 5ghz band I can get a higher throuput typically around 55mpbs. I can understand why it may be slower on the 2.4ghz band but it is completely throwing me why a wired connection should be slower. Have tried different network cables (Cat 5e) and no difference.

Tried to install John's fork but then I can't get tethering...

USB Tethering Speeds - ASUS RT-AC66U