Install nightly to partition

You can register an anyboot image from Terminal via “diskimage register {name-of-anyboot}”. Then mount as usual and use Installer.

The issue seems to be that you can’t install a current nightly from an ancient Haiku installation. The Installer/makebootable etc. don’t know about the package anagement intricacies.
You’ll have to make one last clean installation by creating a USB stick or CD from a nightly. After that you can use the new update mechanism.

Regards,
Humdinger