Maybe 
My problem was that I was reading the topic in the original language. Then I used the toggle, because I don’t speak Chinese. That took me back to the first post (I don’t fully understand why; it doesn’t always happen. That’s why I chose scrolling in the steps above).
And then the first 20 posts were in English, but the last ones were still in Chinese.
I think in that case, a show-original: "false" would be what I needed to see all posts in English. I haven’t tried it the other way around or checked the requests. I haven’t found a replacement for the Kiwi browser which allows using dev tools on Android.