Hi @BenoitG, are you trying to access to eDiscovery with Microsoft Graph API or Microsoft Graph Security API? With Graph Security API, you can access information such as security alerts from Microsoft security providers such as Office 365, Azure Security Center, etc.
This techcommunity forum handles responses to Microsoft Graph Security API related questions. For questions related to Microsoft Graph API, please submit the question on Stack Overflow and tag with Microsoft-Graph, or related techcommunity forum for eDiscovery. Thanks!