If you've found the following limitation through the API where Private Channels in a given Team cannot be listed by a Team Admin due to access restrictions in the API

"Get Public Channels For Team" API endpoint currently requires permission listteamchannels in order to list Public Channels within a team.
https://api.mattermost.com/#tag/channels/operation/GetPublicChannelsForTeam

"Get Private Channels For Team" currently requires permission manage_system in order to list Private Channels within a team. That permission is restricted to System Admins.
https://api.mattermost.com/#tag/channels/operation/GetPrivateChannelsForTeam

Per Mattermost Permissions, a manage_system is a permission that is only assigned to System Admins
https://docs.mattermost.com/onboard/advanced-permissions-backend-infrastructure.html

As a Team Admin, I would like to generate a list of Private Channels within my team and retrieve their information. However, I cannot use the API point to list the Private Channels within my team. It seems that the permission is a tier higher than what it should be for this API point.