They both use MediaTek MT7905DAN n MediaTek MT7975DN as wifi chip n MediaTek MT7621AT at cpu
They both have 128 MiB of flash n 256 MiB of ram
The difference between them is ax53u have 1 x usb port n 3 x lan port n ax1800u have 0 x usb port n 4 x lan port n different LED configuration between them.
becuae of the similarity of them i think openwrt image for ax53u might work on ax 1800hp so i flash the openwrt image for ax53u to ax 1800hp .
Openwrt booted on ax1800hp. it work fine (expect for broken LED configuration n wan port dont work n lan port 4 become the wan port)
Edit : is lan port 4 not lan port 1
Edit2 : i was wrong the the flash layout r that same between them.
Edit3 : NOTE : openwrt now support ax1800 (ax54) so this hack atin needed (see OpenWrt support for Asus AX1800HP)
Hmm It seem only the power led can be only controled by openwrt.The wan led work but there r seem to be no way to control it.Also the lan led has become the network activity led of lan port 3.
I notice it might possible to get the wan port working at a lan port by using older image of openwrt's ax53u image because the device tree of the older image of openwrt's ax53u's drive tree r missconfiged to have 4 x lan n 1 x wan
(yes i know i could rebuild the kernel that have the device tree that configed to have 4xlan 1xwan)