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

https://github.com/atk/void-packages patch-1
https://github.com/void-linux/void-packages/pull/18530

slack-desktop: fix missing dependency
Without xdg-utils, the login will not work so slack basically becomes useless.

A patch file from https://github.com/void-linux/void-packages/pull/18530.patch is attached