I’ve created a test user and placed it into a nonAdmin user group.
I have created a Site Images media source and configured the basePath and baseUrl settings to point to the Site Images folder. I added the nonAdmin user group on the Access Permissions tab.
On the Access Control Lists > Update User Group > Permissions > Media Source Access, I have added the Site Images media source.
The test user cannot access the media media source via a MIGX TV. Both the media source and TV were created before the user profile was.
I created a new image TV and associated it to the Site Images media source. The test user has access to the media source via the TV.
I don’t know if the issue is with MIGX or the media source, but something about the user being created after them is preventing access.