We have few dependencies that require some changes to be made by hand. As far as I know, the dependencies are installed during the EAS build, on the expo servers. I’ve found some partial solutions: private npm packages or using the patch-package tool (not even sure you can run such tool during the build).
I have used patch-package. It works fine with EAS Build. The build just runs yarn or npm install, so as long as you have the postinstall script as per the patch-package documentation it should work fine.