Hi, ThatRandomTechGuy
Welcome to the Microsoft community.
If the operating system cannot be found, it means that Windows cannot locate the boot loader, which has led to your current situation. To fix the boot loader, you need to create a Media Creation Tool (MCT) and then use the BCD command to attempt to repair the boot loader. The specific steps for using the BCD command to repair the system boot loader are beyond the support scope of our forum. You can seek further assistance on Microsoft Learn.
You can also try In-Place upgrade to fix it.
In-place upgrade which will refresh your Windows files and operating system without removing files or applications. That being said, we always recommend that if you have important data, you should back it up before making large system changes. If you want to back up your data first, please do so. Once you are done backing up, you can follow the steps in the following guides:
How to run In-place upgrade in Windows 11 - Microsoft Community
Best regards
Tommy Jin | Microsoft Community Support Specialist