For a governance purpose, you may want to restrict Private Channels creation for user and make available only through the ones you define in Templates. Users won't be allowed to create a Private Channel for any other purpose. Private Channels will be created only with the teams created through the defined templates.
If you want to know more avec Private Channels in Microsoft Teams Templates by SalesTim, learn more in the dedicated article.
The only thing you need to do is first, to disable the ability for users to create Private Channel, second, make sure that only SalesTim App can create private channels.
Disable the ability for users to create Private Channel
As a Microsoft Teams Admin or Global Admin, go to the Microsoft Teams Admin Portal go To Teams > Teams Policies > Select Global > Disable.
As a result, everyone in your organization won't be able to create private channels.
Only Salestim App is allowed to create private channels
Create a new policy that can call for example "Salestim Service Account".
Then select the policy and apply this policy to the Salestim Service Account in your tenant.
Here the Service Account Name is "Salestim", in your organization it certainly has another name that is defined.