Another AX86U. You do not really need the 2.5 GB port(s). A solid 1 GB Ethernet backhaul can out perform the WIFI.
Or an AX86U Pro for the main router and use the AX86U as an AiMesh node. Works well for me and I have the 2.4 GHz set to 20 MHz and the 5 GHz set to 80 MHz. Both on auto channel no DFS.
Oh, FWIW, I've had connection issues with the 2.5 GB router port to the 2.5 GB AiMesh node port.