If the Authentication tab is not available in Standard Logic App, then you won't be able to set up an Identity Provider for OAuth 2.0 security. In this case, you will need to use a different approach to secure your Logic App with OAuth 2.0.
One approach is to use Azure API Management (APIM) as a gateway to your Logic App. APIM supports OAuth 2.0 authentication and authorization. You can set up APIM to authenticate requests from your client applications using OAuth 2.0 tokens issued by your identity provider.
To use APIM with your Logic App, you can create an API in APIM that points to your Logic App endpoint. You can then configure OAuth 2.0 authentication for the API in APIM using an Identity Provider. The Identity Provider can be an Azure AD tenant, or any other OAuth 2.0 provider that supports the required authentication flows.
Once you have set up OAuth 2.0 authentication for your API in APIM, you can secure your Logic App by making it accessible only through the APIM gateway. This ensures that all requests to your Logic App are authenticated and authorized using OAuth 2.0 tokens issued by your Identity Provider.
You can also create custom policies in APIM to further control access to your Logic App, such as rate limiting, IP filtering, and request validation. These policies can be applied at the API level or the global level, depending on your requirements.
Finally, you can share your secured Logic App with other users within your organization by providing them with the API endpoint URL and the OAuth 2.0 token endpoint URL. They can then use these endpoints to authenticate and authorize requests to the Logic App using their own OAuth 2.0 tokens issued by your Identity Provider.