HiNative is a good place to ask language learning questions
The format is simple. You post a question. People answer it.
Questions tend to be very basic - "how do you say 'dog' in Esperanto?", "does 'Mi lavis dufoje miajn manojn' sound natural?" There are templates for asking questions. Answers from self-identified experts are marked differently. I check the site for questions periodically. (I have been meaning to set a reminder to check it at certain times - so maybe now's a good time for me to do that.)
It has a really nice feature that it allows voice questions and voice answers, so if you'd like to hear the answer, this is a great place to ask for that. (I love giving voice answers!)
With the "activity stream" in limbo on Duolingo, now might be a good time to check it out. If you post a question to "discuss this sentence", why not paste the same question (with the sentence you're asking about) over at HiNative?
HiNative was also mentioned in these previous discussions.