There is a new pull request by fosslinux against master on the void-packages repository

https://github.com/fosslinux/void-packages obnam-delete
https://github.com/void-linux/void-packages/pull/14467

obnam: remove
It was retired over two years ago: https://blog.liw.fi/posts/2017/08/13/retiring_obnam/

On the home page:

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The Obnam project is retired. See https://blog.liw.fi/posts/2017/08/13/retiring_obnam/ for more information. Please use another backup solution instead.

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A patch file from https://github.com/void-linux/void-packages/pull/14467.patch is attached