If you want to add a 2.5 GbE interface to your AX88U , you might want to know about this post: https://wu.renjie.im/blog/network/ax88u-nbase-t/
which is somewhat being discussed here:
https://www.snbforums.com/threads/usb-to-2-5gbe-adapter-on-ax88u.67402/page-9
However, I only see the benefit...