https://github.com/autopkg/n8felton-recipes/blob/eb48f762fb351ee98554aae14b519a020dd87bab/Chimera/Chimera.download.recipe is outdated, Chimera is being replaced by ChimeraX (which is universal, yay!) -> https://www.cgl.ucsf.edu/chimerax/download.html
I would have loved to provide a pull-request with a ready solution, but could not make it work yet.