Why are the latest versions of LibreWolf and Firefox browser not using the windows user agent spoofing on Linux. the latest versions of firefox/librewolf reveal Linux as real OS when they previously spoofed it as windows?

[any1]

This was also changed in the Tor Browser and was answered here.

@TorProject

We are still protecting user agents: Tor Browser has always limited user agents to general categories: Windows, macOS, Linux, or Android in JavaScript, and Windows or Android in HTTP Headers. That means we spoof the OS version and architecture, which was always the approach in JavaScript–now it’s consistent in HTTP headers too.

Any OS info shown in the user agent does not expose any new information that wasn’t already present with JavaScript. With JavaScript disabled, entropy is already greatly reduced (self-information: e.g. the thousands of JavaScript derived metrics) and even without this change, passive methods have always existed to determine the platform. In fact, asymmetric user agent spoofing triggered anti-fraud and bot-detection scripts breaking websites without added privacy benefits.