Asus.com will work soon. When you're on that site, please use the "report" link in extension's menu (next to the address bar usually) - you'll see then that I have already checked it and prepared a fix :)

It used to (and still could) work in regular Firefox for Android but Mozilla team decided to stop supporting all extensions (they now allow only a couple of handpicked extensions).

It works in "Firefox Nightly" though, but the installation procedure is a bit complicated. I tried it and it works well: https://blog.mozilla.org/addons/2020/09/29/expanded-extension-support-in-firefox-for-android-nightly/

Are you sure? I just tried it and the website works perfectly. Please report to author@i-dont-care-about-cookies.eu if you see a problem there (or anywhere else). Thanks :)