Someone else has mentioned CreditLadder and I can confirm it works with Monzo - my rent is reported to Experian.
There’s a few replies that rent is not credit so does not affect your credit score that are factually incorrect. Rental reporting is opt-in only, so the impact on credit scores is not likely to be high but some credit reference agencies are taking it into account to allow people to improve their score. The slightly worrying part is that to do it, you grant access to your transaction history - which, if CreditLadder are unscrupulous, could be used beyond the scope of just rent.