Recently, I had a video about PHP CS Fixer's ability to override coding standards locally, and how the docs even encourage having a local config file which is untracked to let you do this.
I couldn't understand why you want to do this, since it seems to defeat the purpose of having a shared coding standard in the first place.
The creator of PHP CS Fixer had a great explanation I wasn't considering.
There are other things you can adjust in these files besides the actual coding standards: the path to your PHP executable, cache location, how progress bars are shown, to name a few.
Some of those things you might standardize as a team by using Docker, but some could just be personal developer preference.
He also agreed it would not be a good idea to override actual rulesets and coding standards this way. So my original point stands, with this additional nuance that there are a few settings that could make sense to override locally.
Here to help,
Joel
P.S. If your project doesn't yet have a coding standard, I can help you get that set up quickly so you can enjoy a cleaner codebase. Just get in touch.