Though it may have worked when the restriction was not added, this installer is not intended for access points. It is specifically designed to hook into the "router" in router mode.
The original intentions or design of the installer were intend for this purpose, thus why the restriction was added.
If you wish to set it up you can follow one these guides and adjust according to your setup.
I have finally managed to install AdGuard Home on an Asus Router.... this is without using any special scripts. There was a previous forum post (here) on the same, but that involved installing using a custom script (that asked for your ssh login credentials, installed its own version of Samba...
www.snbforums.com