Most have the following trope: pretty boy captured by the emperor/prince and forced to be a concubine.  Others marry due to imperial decree.
Some harems. Some dubious/non-consent, but not always. I will note if it's consensual.

I annotated the ones I read. Those are on top. The most recent books I found are on the bottom.

Also Recommended: "The Captured Crown Prince" aka "The Prisoner of the East Palace" aka   东宫阶下囚 by 作者:六妖.  https://www.sto.cx/mbook-186546-1.html. (dubious/non-consent).

Do a Google search of Chinese name in Chrome so you can read with Google translate.

My other danmei list: https://www.novelupdates.com/viewlist/54013/?ft=yes

Enemies to lovers; arranged marriage; forced marriage