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

https://github.com/krkk/void-packages fix-mumble-plugin
https://github.com/void-linux/void-packages/pull/27065

mumble: fix plugin path
https://github.com/mumble-voip/mumble/blob/1.3.3/src/mumble/Plugins.cpp#L212-L220

Mumble was searching plugins in `/usr/bin/plugins/` because `MumbleApplication::applicationVersionRootPath()`(basically the `QCoreApplication::applicationDirPath()`) returns the path of the application executable.

A patch file from https://github.com/void-linux/void-packages/pull/27065.patch is attached