https://www.novelupdates.com/series/the-disabled-tyrants-pet-palm-fish-transmigration/ Mute ML Spoiler: Caveat ML is cured of the condition that led to his mutism toward the end of the story.
Seconding "The Disabled Tyrant's Pet Palm Fish," it's a wacky premise but really grabbed me! And it was a nice change of pace to have a danmei novel where the guys weren't going through a sexuality crisis, they're both comfortable with liking other men from the start. Although - spoiler warning, mentioning in case this is a deal breaker for you: Spoiler the muteness does eventually get cured, but it wasn't a major goal for most of the book since nobody thought it could be cured, and the main love interest has accepted it as part of his life since a young age and found ways to work with it, so it's thoughtfully incorporated/accommodated for and not milked as a source of angst or anything.
Not fully mute, these mangas & animes got people w/ speech impairment due to hearing disability: Gangsta (no rom) Koe no Katachi Kingyousou Kimi no Te ga Sasayaite Iru (old '90s manga, no ENG translation AFAIK)
I have manga for you, if that's okay? Kimi no Koe (mute fl from trauma) Yubisaki to Renren (the fl is deaf so she doesn't really speak... does that count as semi-mute? )