Best Way to Get Real, Organic YouTube Subscribers?

For an already existing account with good content, what are the best ways to get real, organic subscribers, preferably USA ones? What options exist?

Does something like mother-child (used for IG) exist for YouTube? Is there such thing as automation tools which show your account to a target list via interacting with the accounts on the target list, etc.?

I’m very familiar with the various IG growth methods but fairly clueless on ones for YouTube and I’m curious if any such IG ones also work for YouTube. With IG, you can order real organic followers by the thousands in many ways such as mother-child but this doesn’t seem to exist for YouTube. From a cursory look, it seems promoting videos or a channel via Google Ads is the only viable thing.

Can you help me with the IG part, what method do you use for viral, because I haven’t been able to do it for a while.