https://wicg.github.io/ua-client-hints/#sec-ch-ua-wow64

Website seems to not yet document the Sec-Ch-Wow64 header.

Chromium-based browsers have it since v100 (including chromium android).
Webview also has it since v100.
Firefox and Safari not yet.
Opera has it since v86 (version that it ships with chromium v100)