Error: 'rhel-7-server-devtools-rpms' does not match a valid repository ID

Hello!
I'm trying to install llvm-toolset as explained here:
https://access.redhat.com/documentation/en-us/red_hat_developer_tools/1/html-single/using_llvm_9.0.1_toolset/index

but getting error:
subscription-manager repos --enable rhel-7-server-devtools-rpms
Error: 'rhel-7-server-devtools-rpms' does not match a valid repository ID. Use "subscription-manager repos --list" to see valid repositories.

I am using no-cost developer subscription for individuals.

--
sudo subscription-manager attach --pool=8a85f99c7db48285017e0a6ec42d5c3a

Successfully attached a subscription for: Red Hat Developer Subscription for Individuals

Below grep is returning empty:

subscription-manager repos --list | egrep devtools

--
subscription-manager attach --auto

No Installed products on system. No need to attach subscriptions.

I've unregistered, re-registered, refresh, yum clean all. But nothing works.

This machine is Amazon Linux 2.

Linux .compute.internal 4.14.256-197.484.amzn2.x86_64 #1 SMP x86_64 x86_64 x86_64 GNU/Linux

Please advise.

Thanks!