After your WLWN523N2 firmware work, if the system boots but behaves erratically, you need runtime debugging.
setenv bootcmd 'if nand read 0x80000000 0x200000 0x500000; then bootm; else nand read 0x80000000 0x800000 0x500000; bootm; fi' wlwn523n2 firmware work
If U-Boot is corrupted, you need JTAG. Connect your programmer to the JTAG header (TCK, TMS, TDI, TDO, TRST). After your WLWN523N2 firmware work, if the system
Clone OpenWrt and add support for WLWN523N2: After your WLWN523N2 firmware work