The official English is on Tappytoon! The mature version can only be accessed on the website- not the app.
https://www.tappytoon.com/en/comics/deardoor-m
There will not be any smut/smex because this is a Chinese comic. The laws in China ban depictions of homosexuality, so any manga from China will always censor kissing, never show sexual encounters, and censor anything else that might go against the law. No one would want to be arrested for drawing two guys being intimate.
It’s still possible for a Chinese creator to create spicy scenes and post them somewhere else. They might just be Chinese and not live in China, or maybe they use a VPN and post to Twitter- which is blocked in China. But artist that try to post even guys kissing can get in trouble and so it is usually censored. Just depends on how much risk the creator wants to take, but how much risk would you want to take if your crime in a prison is for art?
Where might one be able to read the novel? Sadly I can only read English though if it’s only in Korean or another language. It’s just, the story is so good I want to read more, and I wouldn’t mind looking at the novel