Q: “How can I see all Permission Sets assigned to a user, regardless whether they’re assigned directly to the Permission Set or via a Permission Set Group?”

A: It’s weird how tough this is.

• I recommend voting for this IdeaExchange Idea, which asks for this:

. . . there’s some ability to do this with Salesforce’s newish “View Summary” button, but it’s not the same (here’s my rant, if you’re interested).

• I’ve been noodling with SOQL, and come up with this:

SELECT Label, Type,
      (SELECT PermissionSet.Label, Assignee.Name
       FROM PermissionSet.Assignments 
       WHERE Assignee.Name = 'USERNAME'),
      (SELECT PermissionSetGroup.MasterLabel, PermissionSet.Label
       FROM PermissionSet.PermissionSetGroupComponents
       WHERE PermissionSetGroupId IN 
            (SELECT PermissionSetGroupId 
             FROM PermissionSetAssignment
             WHERE Assignee.Name = 'USERNAME'))
FROM PermissionSet
WHERE Type = 'Regular'

. . . which returns goodish output in Workbench (albeit with empty rows), but looks ugly in Salesforce Inspector Reloaded or Developer Console:

• Reporting doesn’t cut it, either. I think the proper answer is gonna be Flow or Apex code. Reply to this post if you know a solution that 100% solves this need!