asuswrt-merlin
on SourceForge
RT-AX58U/Beta/RT-AX58U_384.16_beta1.zip
RT-AX56U/Beta/RT-AX56U_384.16_beta1.zip
RT-AX88U/Beta/RT-AX88U_384.16_beta1.zip
RT-AC86U/Beta/RT-AC86U_384.16_beta1.zip
RT-AC5300/Beta/RT-AC5300_384.16_beta1.zip
asuswrt-merlin
on SourceForge
RT-AC3100/Beta/RT-AC3100_384.16_beta1.zip
RT-AC88U/Beta/RT-AC88U_384.16_beta1.zip
RT-AC68U/Beta/RT-AC68U_384.16_beta1.zip
RT-AX3000/Use the RT-AX58U firmware.txt