There is an updated pull request by damadmai against master on the void-packages repository

https://github.com/damadmai/void-packages mosquitto163
https://github.com/void-linux/void-packages/pull/12552

mosquitto: update to 1.6.3.
Also added runit service as unprivileged user for it

A patch file from https://github.com/void-linux/void-packages/pull/12552.patch is attached