Apple now lets you sync your passwords with Firefox, but not on Windows
If you do need to access your iCloud passwords on Windows, you can access them by downloading iCloud for Windows and the iCloud Passwords extension for Chrome or Edge instead. We’ve asked Apple if it plans to add support for Windows to its Firefox extension.
Another developer originally made the Firefox extension, but Apple has taken it over, according to a notice on the extension’s GitHub page. Apple is “now the sole owners in charge of maintaining their own official iCloud Passwords extension,” the developer says. The extension’s repository and source code aren’t linked to it anymore except for “historical reasons.”