As far as I know, the end-users can install apps on their own if the app permission policy lets them install it and the app is allowed by the Teams admin. If an app is blocked, then end-users can request admin approval.
To install apps using an app setup policy, follow these steps:
- Sign in to Teams admin center and access Teams apps > Setup policies.
- Select Add.
- Provide a name and description for the policy.
- Under Installed apps, select Add apps.
- In the Add installed apps pane, search the apps that you want to install for users. You can also filter apps by app permission policy.
- Select Add.
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