Currently, 1Blocker is available in nine languages. You can switch between them by changing their priority in the iOS/macOS settings.
On iOS, you will need to go to the iOS Settings app > 1Blocker > Preferred Language.
On macOS, it is necessary to go to macOS System Preferences > Language and Region > Apps > 1Blocker, and choose the preferred language. After that, you will need to restart 1Blocker, so that it can check the language and change it.