SCAN requires DNS
Not exactly. Yes, it's strongly recommended, but assuming yours is not a production environment, you can use hosts file on each node and each client.
I put entries in the hosts file of both nodes, installer proceeds with SCAN warnings and EM does not work.
I think now I should follow the doc which you have sent.
You should be able to install Oracle Grid Infrastructure without DNS. As mentioned, you should configure the /etc/hosts file on each node before you start the install. I should configure Public, Private and Virtual in your /etc/hosts file.
I've implemented Oracle RAC 10, 11 and 12c without DNS and it works fine. There is some additional configuration to be applied since you are not using DNS.