I was recently camping on a farm and faced a similar problem with trying to use the Beryl AX as a repeater with no amount of MAC cloning, DNS changes…etc working at all and I could not believe that their system would have been sophisticated enough to block the router in the way you have described. Furthermore, trying a different make worked straight away and with no fuss at all leading me to the conclusion that there is undoubtedly an inherent issue with the GL.iNET’s abilities to repeat WiFi and/or deal with captive portal.