@BDM That's a suggestion for convenience. If it is in the DHCP range is possible that the router will give the same IP address to another device (by DHCP) which will cause an IP address conflict.

@Itsame Contact your local support, explain what you've done so far and ask them how to proceed further.

@Blue-whale 2.4 GHz band doesn't support AC standard. What's misleading you is when Smart Connect is active, both bands (2.4GHz & 5GHz) are emitting wireless signal with the same SSID.

@sammy2091 Is that what you're after:

@ReGen I've seen cases where the static route is still active after reboot but not in the routing table. Check that after rebooting the device (pinging the device in the other subnet). If that's not...

@realsyntech For a PiHole set its IP address here: