How else could they get to know that if the whole topic is taboo?

Well, it's not a taboo (at least I've read it as if the person is just tired of it).

But generally you can just ask something like "Will it be fine with you if you I share a piece of advice?"

This works even better if you tell why you think this might be relevant at all (for example if you have some expertise or have a very similar experience yourself).