Oh my god, the app language feature got added in the last update and it set itself to "arabic" by default because it's the first in the list, but since there is no arabic localization it just puts english text in right to left
Hey there! Sorry for the late response, but what you mentioned was correct. By default, Thunder will try to get your system's locale and set that as the default. However, in the cases where Thunder cannot get your system locale, it will default to the first language (which happens to be Arabic)
To solve this issue temporarily, you can go to Settings -> General -> App Language, and set the language appropriately. This is the GitHub issue related to this: https://github.com/thunder-app/thunder/issues/929