Hi
I replied by email but I'll post here so anyone can get help about this in the future.
Steam stopped subscriptions (I'll release an update with the subscribe button removed on steam so it doesn't create confusion). As many pointed out, all you need to do is download from any other store. I can be Microsoft Store, Google Play or Apple. From there you can subscribe.
Second step... I don't know my email or password. Well, if you have the game right now on any device, just go to the world chat screen. Under your name there is an "edit" button that allows you to change your pilot name AND your email. So there you have your email.
Go into your new installation, use that email. If you don't remember the password, hit "forgot password".
If you don't have access to that email any more, just change it with that "edit" button.