Undo Changes to Boot Files Caused by Mounting Disk in Another Instance of Windows

I have a laptop containing 1 SSD and 1 HDD. The laptop had a power issue and I took it to a repair shop. I kept the disks with me, and because the repair shop just kept delaying starting work on the laptop (suspected blown capacitor), I bought a new Windows 11 laptop, and a SATA to USB cable with to transfer over the data. I encountered a problem though when doing this, and so when I got the old laptop back (which was now working even though the repair shop didn't even do so much as open it up), I put the disks back in to try to recover my data that way. However, now it's not booting and the UEFI is failing to notice a bootable device! Could somebody help me please?

The SSD was the bootable device, carrying Windows 10, and when I connected it to my Windows 11 laptop, I could mount it and read it perfectly fine.

The HDD was holding the vast majority of my data and contained an encrypted partition, and non-contigous partitions. It wouldn't mount when connected to the Windows 11 laptop and Disk Management showed it as "Invalid Dynamic Disk".

Really, its the HDD that I want to recover data from, but because it's a dynamic disk (something I had never heard of until this all started) I don't think data recovery tools would get me very far, especially with the encrypted partition. I regret connecting the disks to the Windows 11 laptop.

What I would like to do is undo whatever I did to the MBR or drive signature of the SSD, but without erasing the instructions it must hold (the partition table I suppose) for the HDD. It seems like a very difficult problem to solve, but I thought I would ask the community. I haven't tried repairing it using Windows 10 installation media repair yet because I'm scared it will make things worse. I did find a video that looked like it might be helpful called "Windows 10 and 11 Wont Boot, How To Fix UEFI Partition" by CyberCPU, but again I'm not sure if that's going to make things worse because he doesn't mention the 2 disk setup.If anyone has any ideas then I would be grateful if they could let me know! Thanks!