Not working cards perfectly work on another boards: MT7621 with PCIe, Marwell Feroceon 88FR131 and x86 boards.
What different PCB desigh RV2 board or software bug?
If possible, please separate this message into another discussion. Thanks.
Maybe its due to power draw ? Some cards have higher power requirement than others. Some issues were observed with certain NVMe because of that on the B key slot. I suppose the same may apply to the mPCIE slot, but not sure. The mPCIE cards I tested all worked fine.
Make sure your OpenWrt build has the right firmware / drivers enabled !