Thanks for the suggestions! Unfortunately we cannot just uppercase our filenames since we also have to upload these files to external project banks and they are actually case-sensitive.
I will have to create a new ZFS volume with casesensitivity=mixed. This will avoid conflicts with existing files that have different cases while providing compatibility for AC when it asks for an existing file with a different case.
I noticed that AC 18 doesn't mention case-insensitivity in
system requirements. Can someone confirm this?