In addition to your possible solutions:
I'm a software developer and therefore a lot on technical forums, such as the MicroFocus support forum. As soon as you start a new topic there and type the first words in the "Subject", a small window appears immediately which points you to similar posts like yours. Such a feature would be a huge improvement for the forum and would definitely reduce the number of always the same questions and topics.
I propose the admins to please give such devs (afternoon checking their eligibility and credibility) a chance to work it out as this is something really needed on the forum. I guess the newer version of the forum also doesn't have these features (haven't tried it though), so adding them to the forum will work its charm to help stop spam going on all over the forum.
These solutions will be valuable if people want a useful discussion, where the same topic can repeat but with different content.
That's fine, but then an explanation needs to be given.
One more thing here, even if the question is same and OP inputs different material, then instead of looking the first page, many users directly go for the subject and reply accordingly which makes that thread a megaspam one.
Re-repeating, the same question without searching, is an attempt to get extra activity points without effort "SPAM."
So the solution is to make the activity worthless "as happened by activating the merit system" and over time will reduce profits /participants.
Until then, reporting posts is the best solution.
No matter how we try to describe them, I've always seen many newbies (mostly alts) asking the same questions with almost same content and then their major accounts show up giving same or a bit different replies to give a green signal to the thread, and then everyone goes on and on until it reaches tens of hundreds of pages with hell shit of spam.