This does not happen with any other chromium based browser
My phone locale is set to Italian with English as second language. IP address is Italian. I’m not understanding why sites like f-droid, Google dev documentation, gitlab, are all defaulting to Chinese as I can’t read it…
Sometimes I can find a link to switch back to either English or Italian, but the next visit they revert to Chinese…


At the beginning of your post, you wrote that “This does not happen with any other chromium based browser”. This would indicate that it’s a unique problem to Firefox and would in turn be a Gecko engine issue. Now, if this was an issue with other browsers, then I’d agree with you.
After investigating, it’s because chromium browsers don’t send “zh-Hans-CN” in the request header and it turns out that many server side language detection implementations are buggy.
So, it’s not technically a Firefox bug, but, considering the minuscule share of people that are
It’s extremely unlikely that hundreds of separate website owners will fix their implementation
I’m guessing the people with this issue are in the orders of dozens, not thousands