Sorry it took me so long to get my post up. And I'm sorry that the letter to Rhaenyra isn't actually attached (I just went full-on block out mode and couldn't think for shit) but the summary would be that Talron pledged his support for her claim, and asked that she recognize and do all the can as rightful heir to the Iron throne to protect Talron's sovereignty of the Iron Islands, and in exchange he'll do all he can to get her on the Throne.