juha
11
Thanks @Johnex! Your link did lead me to the third thing, DNS encryption to be disabled and now getting the portal popup!
So, all good and not going to need custom firmware 
Just a note if anyone else having the ”issue”.
- Disable all VPN connections in the router.
- Disable DNS rebind protection. This is generally true but not for all portal.
- Disable DNS encryption. In GL.iNet routers there are CloudFlare DNS.