Customize helm chart from stable repository
You don't necessarily have to push to your own repository as you could take the source code and include the chart in your own as source. For example, if you dig into the gitlab chart in their charts dependencies they've included multiple other charts as source their, not packaged .tgz files. That enables you to make changes in the chart within your own source (much as the gitlab guys have). You could get the source using helm fetch stable/traefik --untar
However, including the chart as source is still quite close to forking. If you want to upgrade to get fixes then you still have to reapply your changes. I believe your only other option is to raise the issue on the official chart repo. Perhaps for your case you could suggest to the maintainers that the ingress be included only when .Values.dashboard.enabled and a separate ingress condition is met.