Just in case, it is still possible to disable the timeout by removing the timeout attribute. I didn't encounter a hardcoded 600 seconds timeout when I tested that on my side.

You can find the language because you can check: that the installation is not run from installer(8) or a deployment solution such as Apple Remote Desktop. which user has requested the installation through the $USER env var. From there you can find the language preferences for the user (unless the root user can not check the contents of the Library/Preferences folder anymore…)