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

https://github.com/CameronNemo/void-packages fceux
https://github.com/void-linux/void-packages/pull/27646

fceux: update to 2.3.0.
This switches the GUI from GTK3 to Qt.
GTK3 is still available, but did not work fully in my testing.
Qt is the default and recommended GUI, and it worked.

A patch file from https://github.com/void-linux/void-packages/pull/27646.patch is attached