Thread already exists: https://forum.novelupdates.com/threads/the-elegant-dukes-training-method.133282/
Unfortunately I can only give you one thank,I knew it wasn't my imagination when I thought there was already a thread about this story,but I just couldn't find anything...thanks a lot,you just made my day
Spoiler: Official manhwa translation https://www.tappytoon.com/en/comics/lessons-in-seduction-with-a-classy-duke-m
Before he met Lillian he did seem to sleep with others, orgy stuff like that. But after that he stayed loyal to Lily. The photos Lily saw were meant to be seen by her, it was captured for the purpose of being 'sent' to Lily. He did attend bars while they were married to WATCH, just WATCH them, even saying Lily's name while imagining. He also confessed he tried to whip a woman imagining it was Lily, but he couldn't bear to do it with someone else so he only did it that one time, and he never did it again. This has 17 Chapters as of May 16, 2022. I read it in Coffeemanga.com, as of April 3, 2022 it has 30 chapters
I was impatient too and ended up buying the raws a few months ago. I can’t remember exactly where 28 left off but in chapter 29 I’m pretty sure the ML and FL just talk/make up and in chapter 30 they just have sex, the end. That was almost exactly how it went.