It works regularly in Mozilla Firefox 129.0B9 X64. It is a pity that manual editing of a list of comparison of domains and UA is carried out only in JSON format, and not in something more accessible to non-specialists.
Upd. 0.6.6 (Oct 8, 2025) and Mozilla Firefox 148.0b12:
1. Selected "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/142.0.0.0 Safari/537.36" from the list. 2. Clicked "Apply (all tabs)". 3. Clicked "Test UA". 4. webbrowsertools.com: "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:148.0) Gecko/20100101 Firefox/148.0".
