Dunno if anyone noticed, but SimplyTranslate added DeepL as an option for translation through their frontend. Doesn’t seem to work for me, seems to give me “error: Invalid Request” (it’s in testing phase, that’s probably why).
EDIT:
woops, turns out “Autodetect” was the culprit. Try choosing a language instead of leaving it default to “Autodetect”.
SimplyTranslate does adjust the list of available languages (to and from) depending on which translation engine you selected, the one with the most available languages is obv Google