The only organization worth actually "joining" and paying an annual fee to is Editorial Freelancers Association. It's based in NYC, was started by two editors in 1970. It has a great reputation among the businesspeople and artists that use the organization to find freelancers of all editorial types - including graphic designers, indexers, writers, you name it. When you sign up, you put up your profile, the org publishes rates that are reasonable for the buyers of the services to pay. Then you start getting nearly daily emails of clients looking for specific work they need done - and will meet the rates proscribed by EFA.

Any other platform is a complete scam. Count of that. How to find them and read more of their history - https://www.the-efa.org/about/#history

I used it for years. Yes, it is highly competitive and you have to be fast to get in there and make your bid. But you won't find those bullshit clients like you find on Upwork (gah!). I had several repeat clients, one from Germany with the largest company in the country, and they publish sheet music and books about music. I have a music degree and was a perfect fit. So whatever makes you unique, write it down.