I just tried installing it and it went just fine. Also on 1.12.7, installer 1.12.7.
Which version of macOS are you running? I only ask because a lot of Mac users generally don’t run the latest version which can sometimes cause problems when software is updated.
Failing for me as well. I reinstalled Obsidian. Made no difference. There is nothing mentioned in the github repository. I am able to install other templates just fine.
Looks like a build issue with Harper. The latest released version is shown as 2.0.0, but the latest actual version is 2.1.0. There is an existing issue showing this mismatch is messing up more than just Obsidian users, and perhaps explains why some people have it working and others get the 404 error. I blame Github, which is often the source of strange problems.