Overview
When installing the CleanUrl module on Omeka S 4.1.x, the following error occurred.
Laminas\ServiceManager\Exception\ServiceNotCreatedException
Service with name "Omeka\Acl" could not be created. Reason: Resource id 'Omeka\Controller\Site\Page' already exists in the ACL
This issue had also been reported in the following forum.
https://forum.omeka.org/t/error-installing-version-4-1/22522
Solution
The issue was resolved by downgrading to Omeka S 4.0.x.
Summary
I hope you find this helpful.