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

https://github.com/mobinmob/void-packages mtpaint
https://github.com/void-linux/void-packages/pull/20959

mtpaint: update to 3.49.26.
- Use Gtk3.
- Enable webp support.
- Install documentation.

A patch file from https://github.com/void-linux/void-packages/pull/20959.patch is attached