I agree mostly with @ben’s suggestion.
Maybe it is possible to have a “translator group” which can be flagged, just as moderators can be flagged now. E.g.: You click on the flag symbol and then you can choose “Have this translated.”
People can voluntarily offer their help to participate in the translator group in a separate (maybe pinned) topic.
@joe please check out this: @HugoAlmeida from the meta.discourse.org forum wrote a plug in which lets you translate individual post with a button next to the post. Could this be implemented on the Fairphone Forum?
https://meta.discourse.org/t/translator-automatic-post-translation/18756
If it is feasible, it should be one of the options in a poll.