Feature flags are often ridiculously over engineered.

Check a config, bdd value, env var to dynamically go one path or the other.

That’s all, you must either have a small feature or refactor the code to easily switch at a high level.

If you are not able to do so easily, then yes, complex feature flags implementations might help you, to coordinate feature activation between micro services.

Or if you have many features then a dashboard might be useful.

But I would argue that both are serious indicators that you should avoid feature flags, they are better for local and temporary changes, otherwise the complexity compounds and it become hard to manage and maintain.