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

https://github.com/Duncaen/void-packages ffmpeg-srt
https://github.com/void-linux/void-packages/pull/37368

ffmpeg: add and enable srt build option
None

A patch file from https://github.com/void-linux/void-packages/pull/37368.patch is attached