It looks by your ip addr show command, you are trying to do this with Linux. This SHOULD work, but there were some issues with Uboot code not working with Linux on some older products. I own both AR300M and AR300M16 routers, and have been able to use Uboot with Windows 10 to load both GL iNet and OpenWrt firmware.
On Windows 10, I set the PC IP address to 192.168.1.2, and make sure the Ethernet connection is made before power on the router.
I’m not sure if it is the same but for my Flint router I actually do 1 and 2 reversed.
Basicly I do the following:
have ac coord unplugged from the router
add one ethernet cable in lan1
hold down the pin
when i hold it down i connect the ac coord.
then wait the 6s (long led indicator if present)
Then do the static ip configuration like also other ppl said , if i don’t do it in these steps it will not give me uboot the step of when connecting the power and when reset is being hold is very crucial