Issue Summary

Currently, it's not possible to view a comprehensive list of all spaces unlicensed users can access via JSM. 

[...] this permission can only be turned on via Jira Service Management and will override all existing space permissions. This means that any logged-in Confluence user will also be able to see the space regardless of their group membership). 

In Global Permissions, you can disable JSM access across the entire site, but you can't see which spaces have it enabled, in case you want to disable them individually: Manage access for Jira Service Management agents

To disable JSM access, click Edit in the JSM access tab and uncheck Use Confluence. Don’t forget to save changes. Once disabled, JSM access to Confluence can only be enabled again in JSM.

Suggestion

In Global Permissions, or perhaps even Space Permissions, show a list of spaces that JSM allows all logged-in users (any active user) to access.