You can onboard Windows Servers into Intune by using Defender for Endpoint (you would also hybrid join them to the corresponding Microsoft Entra tenant). This would allow you to use device-based Conditional access - as described in https://learn.microsoft.com/en-us/mem/intune/protect/advanced-threat-protection In addition, you would obviously be able to use all of the Defender for Endpoint based functionality, including its integration with Intune (https://learn.microsoft.com/en-us/mem/intune/protect/mde-security-integration)
hth Marcin