I noticed the same thing after the last update. I would also prefer English as the interface language. Before the update everything was in English and now I have a mix of German and English. I already selected English as the interface language on the website but it didn’t change the ones in the app. In the app itself I haven’t found any settings regarding this. I’m sure this is because my device language is German.

It might be reading the lanaguage you are using on the operating system if that’s the case I don’t think you can.

Related issue https://github.com/dessalines/jerboa/issues/755