Only issue with it is that the source code (of the front-end) is quite hairy to understand and modify. I tried to add support for Github Enterprise (https://github.com/jgraph/drawio/issues/473) and was quite lost.
It's a reasonable critism. The base of the stack is a proper dev library. The top part evolved from an example to that library and didn't get the same refactoring love to make it accessible to other devs.
Main problem from our end on your issue is we don't have access to a Github enterprise instance to test anything.
Main problem from our end on your issue is we don't have access to a Github enterprise instance to test anything.