Do what reddit did, use multiple accounts as founders, and with AI I'm sure it's even easier to do so. For content-based platforms you must have content, there is no way around it and I don't see adding fake content in the beginning to be unethical, it is a solution to the cold start problem (also a good book by Andrew Chen at a16z [0]).

[0] https://a16z.com/books/the-cold-start-problem/