What strategies can be used to build a community around your product?

I think it really depends on your product and customer base. If you're selling to seniors, then you probably want to build a facebook page. If you're selling to the younger generation, a discord server might be better. I usually leave comments with value across various social media and link my community when relevant in the same comment.

Build relationships with the type of people who will be your customers. Don't be that person to only show up when you have some kind of a launch.