I can't test on RHEL.

.ansible-lint

@@ -1,3 +1,5 @@
 #
 # Ansible managed
 #
+exclude_paths:
+  - ./meta/exception.yml

README.md

@@ -90,8 +90,6 @@ This role has been tested on these [container images](https://hub.docker.com/):
 |debian|latest|no|
 |centos|7|no|
 |centos|latest|no|
-|redhat|7|no|
-|redhat|latest|no|
 |fedora|latest|no|
 |fedora|rawhide|yes|
 |opensuse|latest|no|
@@ -103,6 +101,14 @@ This role has been tested on these Ansible versions:
 - ansible>=2.9
 - git+https://github.com/ansible/ansible.git@devel
 
+Exceptions
+----------
+
+Some variarations of the build matrix do not work. These are the variations and reasons why the build won't work:
+
+| variation                 | reason                 |
+|---------------------------|------------------------|
+| redhat | Can't test on RHEL: No package matching 'firewalld' found available, installed or updated |
 
 
 Testing

meta/exception.yml

@@ -0,0 +1,4 @@
+---
+exceptions:
+  - variation: redhat
+    reason: "Can't test on RHEL: No package matching 'firewalld' found available, installed or updated"

meta/main.yml

@@ -30,11 +30,10 @@ galaxy_info:
         - bionic
 
   galaxy_tags:
-    - centos
     - firewall
     - firewalld
-    - rhel
     - server
     - system
+    - centos
 
 dependencies: []