Join a Union. The bitter truth is your employer has a lot more lawyers than you do. For all the talk about how well-compensated and in-demand tech workers are, the reality is usually different. You need someone in your corner to help you fight for your rights. If you're a tech worker in the UK, you can get three months free membership at https://prospect.org.uk/join/
Anyone have any idea how this would/could work for a company with employees in many different countries? Especially if the number of employees in your own country is low? (Single or low double digits.)
I've somewhat seriously looked into this a while ago and my main takeaway would be: a) contractors can't unionize and b) you can unionize locally, as long as you get signatures from X% of the employees in your country.
Also, and I can't stress this enough, reach out to some already established union in your own area and ask for advice. You're gonna find out some things that are not easily googleable.