OH, AND THIS ONE https://www.mangago.me/read-manga/yang_il_woo_and_i/
I'll give you a brief description of why they all have trigger warnings for heavy topics.
https://www.mangago.me/read-manga/incidentally_living_together/
Mc has severe depression and he self harms, it has a lot of TW, but the story is so good
https://www.mangago.me/read-manga/solo_for_two_mature/
has a lot of angst but the story is a masterpiece, MC has bdp added to trauma and alcoholism
https://www.mangago.me/read-manga/macguffin/
omegaverse, Mc has depression, suicidal tendencies and ptsd
https://www.mangago.me/read-manga/greeting_you_strangely/
Mc has depression and self harm himself
https://www.mangago.me/read-manga/ouroboros_1/
Mc has ptsd and is not mentally stable after SA

I need more recommendations where the Mc is mentally ill