imo these dramas is not serious, but I'm putting some spoiler warning, don't click it if you don't want spoiler:
- Back to Seventeen (time travel, long-term unrequited love, there's domestic violence but only for a while) - short length
- Destined to Meet You (arranged marriage, hidden intention, kidnapping attempt in the past) - short length
- Falling into You (trainer-athlete relationship)
- First Love (fake relationship)
- Hidden Love (long-term unrequited love, money and life debt as ML's dad unintentionally murder the dad of ML's high school friend causing some bullying taking a small part of the story)
- My Uncanny Destiny (amnesia, rival countries, historical, assasination attempt, ah there's-not a love triangle-but a woman forced her way to become ML's concubine and a man like FL)
- The Best Day of My Life (fake relationship, cohabitation)
- Secrets of Shadows Sect (master-bodyguard relationship, wuxia, there are assasination attempts, poisoning, and there are two men who want to have FL) - short length
- The Love You Give Me (ex-lovers, hidden child, misunderstanding, false accusations)
Not really sure about love triangle though, there are some admirers, a few are crazy for both FL and ML but there's no cheating or affairs.
Short-length dramas are usually less than 15 minutes? You can search for the full episodes drama on youtube, dailymotion, or bilibili so you only need to watch one video.