Msteams-docs: Uploading custom apps is not allowed.

[Ajjos]

Receiving this error while Installing the sample app following this article - https://docs.microsoft.com/en-us/microsoftteams/platform/get-started/get-started-nodejs-app-studio.
Teams App policies won't help as there is no option to allow or disallow.

[clearab]

That is the error you receive when sideloading of apps is disabled for your tenant. Can you try the instructions here: https://docs.microsoft.com/en-us/MicrosoftTeams/enable-features-office-365