In your user settings, make sure “Language” is set to both “English” and “Undetermined”. You can select additional languages as well, but they aren’t currently allowed on this server. On desktop, you can use CTRL+click to select both options. This will allow you to see content for which the author has not set a language, and content which has been set to “English”.
That has not been my experience. I did see a post in French once, but that's it. Can only assume non-English speakers are way better at using their language settings than we are.
I have English, and unspecified checked for my settings. With that configuration, I am not getting inundated with posts that I cannot read. Of the posts I do see, occasionally one will be in German, but I've since blocked that community, so I don't see them anymore.