Because the app is account level, non-admin users outside of your account will have to either have the admin install the App on their behalf or give the user permission the “Marketplace” permission, located here:
Once the permission is granted, the user will be able to install the app with no problem. Here is a developer article that details scenarios where that message may appear:
Based on your use case, it seems the best option would be to publish your App on the Zoom Marketplace. This will allow your product or service to be accessible to millions of daily users looking to connect workflows and discover new tools.
We do not have sample code for SSO however we do have resources you can reference for your implementation. I’ve linked resources below on getting started with SSO and OAuth. You may also want to check out posts from other community members here.
Sample App Web Meeting SDK
Zoom OAuth Sample App
Zoom OAuth Resources context:
https://marketplace.zoom.us/docs/sdk/native-sdks/auth#oauth-with-meeting-sdk
SSO Resources
https://support.zoom.us/hc/en-us/articles/201363003-Quick-start-guide-for-SSO
https://support.zoom.us/hc/en-us/articles/201800126-Signing-in-with-SSO-