Hi Stephen,
You can use the Group Policy Editor to set this option.
1. Press the WinKey+R to display the Open dialog.
2. Type gpedit.msc in the Open: box and click
OK.
3. In the Group Policy Editor, navigate to Computer Configuration/Administrative Templates/Windows Components/BitLocker Drive Encryption/Operating System Drives.
4. Right Click the Require additional authentication at startup policy and select
Edit.
5. Click the Enabled option.
6. In the Options section, place a check mark in the
Allow BitLocker without a compatible TPM option.
7. Click Apply/OK and exit the Group Policy Editor.
More information, please follow this blog:
Securing Windows 10 with BitLocker Drive Encryption
https://blogs.msdn.microsoft.com/mvpawardprogram/2016/01/12/securing-windows-10-with-bitlocker-drive-encryption/
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