You can remove the bitlocker encryption, and turn off secureboot in the bios. Here's a quick how to:
Step 1: Turn off BitLocker and Decrypt Your Drive
- Open BitLocker Management: Press the Windows key, type "BitLocker", and select "Manage BitLocker" from the search results.
- Choose Drive: Select the drive that is encrypted with BitLocker (usually the C: drive).
- Turn off BitLocker: Click on "Turn off BitLocker" and follow the prompts to decrypt the drive. This process can take some time depending on the size of the drive and the amount of data.
Step 2: Disable Secure Boot in BIOS/UEFI
Enter BIOS/UEFI Settings: Restart your computer. As soon as the manufacturer's logo appears, press the key to enter the BIOS/UEFI settings. This key is often displayed on the screen during startup (e.g., F2, F10, Del, or Esc).
- Navigate to Boot or Security Settings: Look for a tab or menu related to Boot, Security, or System Configuration. The exact location of Secure Boot settings varies by manufacturer.
- Disable Secure Boot: Find the Secure Boot option and change its setting to Disabled. Some systems may require you to set a supervisor password before you can change this setting.
- Save Changes and Exit: Save your changes and exit the BIOS/UEFI setup. Your system will reboot with Secure Boot disabled.
EDIT: Once you've removed the encryption and disabled secureboot, you can partition up nobara however you want and dual boot windows/linux.