About app source

Hi @サンデャ 管理者

Thank you for posting question to Microsoft Q&A.

Based on my understanding of your description: You are looking for a way to prevent users within your organization from independently installing applications from the public Microsoft AppSource.

Please refer the following recommendations:

Method 1: Block AppSource for all users in your organization

This is a global setting that turns off access to the Office Store for everyone.

Sign in to the Microsoft 365 admin center with your administrator credentials.

In the left-hand navigation pane, go to Settings > Org settings.

On the Services tab, find and click on User owned apps and services.

In the panel that opens, uncheck the box that says "Let users access the Office Store" and click Save.

It may take a short time for this change to apply to all users.

Please refer the following document: https://learn.microsoft.com/en-us/microsoft-365/admin/manage/manage-addins-in-the-admin-center?view=o365-worldwide#manage-add-in-downloads-by-turning-onoff-the-office-store-across-all-apps-except-outlook

Method 2: Restrict AppSource for Specific Users

Important Note: Moreover, even if the users try to install the Office apps via Office Deployment Tool, the user won’t be able to use the Office apps because the user don’t have the license to use the Office apps.

Open the Microsoft 365 admin center> Active Users> Click on the User> License and Apps tab> All Apps> Please uncheck Microsoft 365 Apps for Enterprise > Save Changes

Wait for some time for affects be applied and when the user re-sign, the user won’t be able to see Install Office apps.

I hope you are able to resolve this issue quickly.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".   

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.