Don't mount into /data/, that's too broad. If you need to load 'gateway config', then mount the things you care about from /data/config/resources/core/ (on your development system) into the container at the /data/config/resources/external/ directory. The external directory is automatically scanned in on gateway startup and treated as an immutable set of resources that the gateway will not ever attempt to make changes to.
Some more context:
The project inheritance situation is different, but you should generally follow the same pattern:
Mount /data/projects/ (or even individual projects within that folder) - don't try to mount the entire data/ directory, because Ignition needs to do certain things there related to the runtime that don't make sense to VCS/store outside of the container.