On my iPhone 12 mini, which was running IOS 14 (now IOS15, but the issue remains), the language is detected wrongly. iPhone has an option to specify different languages, and create a priority list
First I had only “Dutch”. Which made Brave default to English. I was traveling to Ukraine and added “Russian” as the second language. You can then select which language on the phone has the highest priority (which was Dutch). But when starting Brave, everything was Russian instead.
After coming home, I removed “Russian” from the list in my iPhone settings and now Brave is in English again.
Brave seems to be the only app that I have installed that has this issue, so I think the chance is higher the list is not respected in Brave instead of IOS handing over the wrong language.
The Brave version on my iPhone is 1.30.1 (188.8.131.52)