@julien deroche,Thanks for posting in Q&A.
From your description, I know you encountered an issue that you cannot connect to salesforce because of conditional access.
To narrow down this issue, please do some checks.
1.Please provide us how do you configure Conditional Access policy and Activity Details: Sign-ins about Conditional Access.
2.Please check whether the targeted device is correctly register or join in AAD.
3.Sync the device, restart it and check whether the device is compliant, and you can access Salesforce.
4.Please provide the device status in Intune and AAD portal.
Please try above information, if there is any update, feel free to contact me.
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