In the current OCP documentation, I am unable to find sufficiently detailed/informative documentation for installing openshift-logging with the now current Loki stack. Almost all documentation about logging is about the now deprecated EFK stack.
In the 4.10 docs, there was a dedicated page https://docs.openshift.com/container-platform/4.10/logging/cluster-logging-loki.html which is no longer present in 4.11 and later documentation.
This should be fixed!

4.15

always

    1.open docs for cluster logging
    2.look for installation instructions - all about EFK and not about Loki    

Loki docs missing

Loki docs available