There is an updated pull request by q66 against master on the void-packages repository

https://github.com/void-ppc/void-packages toonz
https://github.com/void-linux/void-packages/pull/15863

opentoonz: add big endian patch
This allows the package to build, and to a degree work (brief testing reveals some color issues in some of the UI though the actual main area with the frame renders correctly) on big endian systems.

A patch file from https://github.com/void-linux/void-packages/pull/15863.patch is attached