It is described that you can set the HOST variable with this line:

HOST=$(oc -n openshift-monitoring get route alertmanager-main -ojsonpath={.status.ingress[].host})

However in the Zsh shell  running that command will give this error:

zsh: no matches found: -ojsonpath={.status.ingress[].host}

In order for that line to work on both Bash and Zsh, the JSON path should be wrapped in quotes:

HOST=$(oc -n openshift-monitoring get route alertmanager-main -ojsonpath='{.status.ingress[].host}')

The same can be applied to all similar commands in this documentation.