Here's a bunch more context on this failure: https://github.com/rsms/inter/issues/184 https://github.com/googlefonts/fontmake/issues/581 https://github.com/rsms/inter/issues/200 https://github.com/rsms/inter/issues/210
I'm surprised the fonts-inter package is still using fontmake directly instead of the Inter project's build tools, especially since per https://github.com/rsms/inter/issues/200 it sounds like this could yield incorrect output.