Hello @Mahesh Kurucheti,
I understand you want to list transcripts using Microsoft Entra ID application then you need to create an Application Access Policy and grant the policy to the application so that it can read meeting details.
Initially, I got the same error:
https://graph.microsoft.com/v1.0/users/<UserID>/onlineMeetings/<MeetingID>/transcripts

Hence to resolve the issue, check the below:
Make sure to assign OnlineMeetingTranscript.Read.All
Application type API permission:

Create application policy and grant the policy:
Login as Admin
Install-Module -Name MicrosoftTeams -Force -AllowClobber
Import-Module MicrosoftTeams
Connect-MicrosoftTeams
New-CsApplicationAccessPolicy -Identity Ruk-policy -AppIds "MicrosoftEntraAppId" -Description "Allow access to Teams App"
Grant-CsApplicationAccessPolicy -PolicyName Ruk-policy -Global

Generated access token:
GET https://login.microsoftonline.com/TenantID/oauth2/v2.0/token
client_id: ClientID
client_secret: Secret
scope: https://graph.microsoft.com/.default
grant_type: client_credentials

I successfully listed the meeting transcripts:
https://graph.microsoft.com/v1.0/users/UserID/onlineMeetings/MeetingID/transcripts
I got empty response as I don't have any transcripts:

Reference:
Configure an application access policy using the cloud communications API - Microsoft Graph | Microsoft
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Hope this helps!