Hello, Snipper Myth.
Welcome to Microsoft Community!
After reading what you have posted, I am sure you have already created the corresponding USB recovery drive for Surface Pro 6 by following the guidelines at the link below:
Surface Recovery Image Download - Microsoft Support
If you are unable to recognize the boot option after creating a USB drive, you can refer to the following link to make adjustments to the UEFI options:
Boot Surface from a USB device - Microsoft Support
If it still won't boot after setting the startup items correctly, we have to consider that your Surface Pro 6 has been malfunctioning or damaged in some way.
At this time, repair is indeed one of the best ways, but let me kindly remind you that the regrettable situation is that the Surface Pro 6 was discontinued in May this year, and the related repairs as well as the warranty service have ended. At this point, it's time to consider a new device, and I'd encourage you to visit the Microsoft Store to get a new one! (if you need one)
These are some of the ideas I have provided you with after combining your situation.
Thank you for your support of Microsoft products.
Best Regards.
Leo.L - Microsoft Community Support Specialist