This question already has an answer here:
Referring to When & How did Yoda come to know about the Rule of Two? which is focused on the Legends answer, how did the Jedi come to learn of Darth Bane's Rule of Two if they are believed to be extinct? Is the answer and sources in canon the same as in Legends?
Edit: I don't know why I have to explain why this is not a duplicate, because
- You would think if I mentioned that question in mine, then that means there is something more that I am looking for that that question doesn't answer.
- That question's description clearly asked - and I explicitly mention it here too - for answers from Legends. I am looking for verification if the answers given are also true for canon or if the canon answer is different - neither of which were addressed there.
- The accepted answer, dated to 2013 and lasted edited 2014, is one I've seen long before the EU became Legends. There's no indication if it's still valid in canon, since that question accepts Legends answers.
- The remaining answers date to 2012, including the one mentioning there's none in canon. It's been almost 4 years since then, and a month since Ep VII came out, a lot has happened since then.
I'm seeking a canon-specific verification, that question accepts Legends and the answers do not provide nor seek distinction between either.