Doki Doki Salvation is a Doki Doki Literature Club mod where MC decides to check on Sayori the night before the festival, and talks her out of hanging herself. Monika, meanwhile, has lost her ability to tamper with the game and is not happy about it.
The mod is mostly linear, and focuses on Sayori, but it's fair to all the girls. It ends with Monika confessing to everyone, and a satisfying and believable scene around it. Assuming you choose to spare Monika, the game delivers the happy ending it promised.
Also, slight content warning: there is some (arguably justified) nudity in this mod, as well as a sex scene. It doesn't show anything lewd though, just makes it clear what's about to happen and then cuts to the next morning.
The mod is definitely good. I still have two criticisms:
The scene where everyone's trying to carpool and having trouble fitting and Sayori makes a crude and incredibly insulting comment about the size of Yuri's butt. Sayori would never intentionally embarrass someone like that. While it's true that she's seriously lacking in social tact (as evidenced by her similar remark during her first exclusive scene in the original game), even she would know how bad that would make Yuri feel.
It's mentioned that Sayori ends up taking medication for her depression, and that it's been helping. This unfortunately reinforces a false and harmful way of thinking about depression. But if you've read my arguments on that, then regardless of whether I convinced you, playing the mod isn't going to make you believe anything worse than you already do.
It's also worth mentioning that the way the story punishes you if you don't forgive Monika is really, really stupid. It is totally unbelievable that Natsuki and Yuri left the club. That experience would have strengthened the bond between the club members enormously, but the writers just wanted to drop the anvil that not forgiving Monika is BAD, so they made the story bend over backwards and completely shatter to show you that. It's honestly the worst example of a shoehorned moral I've ever seen. In fairness, not forgiving Monika in that situation is a totally wrong and indefensible choice, so whatever. It's not that big a deal if the story breaks to push a true moral and it's only if you choose the evil ending.