www.makemkv.com

I have a BD disk with small (<5 sectors each, about 60KB total) scratches, and used ddrescue to create an ISO. Using several passes with -d, it was even able to read through the scratches.

However, makemkv now tells me:

MakeMKV v1.9.4 linux(x64-release) started
Using direct disc access mode
The volume key is unknown for this disc - video can't be decrypted
Failed to open disc

I tried the instructions at /faq/item/12, but the option in Preferences "AACS keys directory" doesn't actually exist. How can I rip this disk?

Unfortunately, some of the information needed to figure out a working decryption key was, apparently, "fudged" by ddrescue in its efforts to come up with a viable ISO file. That information is at the front of the data track, close to the hub.

I would try waxing the disk, then reading it; Sometimes wax can fill smaller scratches well enough for the laser to read the data. If that doesn't work, polishing the surface may be the the only hope. You can also tell MakeMKV to do more retries to read each sector.

I'll just try encoding from handbrake directly.
I normally try to avoid directly encoding because it takes forever