Right now, if I’m not mistaken, all topics within a category (with the solved plugin enabled) has the solved plugin enabled are potential questions which could have one post marked as solution.
Our previous forum software had a feature which could mark a topic as question, which would then show some visual information that the topic is a unanswered question and enable the “This reply is the correct” answer button for the original poster (and mods).
That was a great match for your community where only about the half of the topics are discussions and the other half are questions (which hopefully eventually get an answer post).
My feature request is to add an alternative per category setting besides the already existing “Allow topic owner and staff to mark a reply as the solution”, namely “Allow topic owners mark the topic as question (which can have a reply marked as solution/answer)”. Note that it should also be possible to convert a question topic to a non-question/normal topic.