Those are huge software packages, with their own developers, with high code quality and testing standards.
I wish to make some small modifications to the code. Those modifications will probably not comply with the high code programming standards of the main branches, are probably not necessary for the mainstream developers, but I do need them.
Consider those changes as my own sandbox.
How can I create a version of those packages with my own changes without interfering with the main branches and complying with any code standards required by the official developers of those packages, or requiring any approvals for commits?