A Emissária Divina (2024)

This is a Chinese remake/adaptation of 'Splash Splash Love', available on Viki (the other adapation isn't).
It follows the original closely in several ways - heroine goes back in time due to rain, where kingdom is experiencing a bad drought, she arrives in exactly the same way, is mistaken in the same sort of way, becomes a 'eunuch' who serves the king/emperor, and helps him through her modern school-girl knowledge, there's the taciturn and loyal guard, and so on.
It gives its own spin to several things as well, with the heroine's character being similar but also uniquely this actress's (she's great, especially as the 'eunuch'), the hero being similar but also unique, with his own character/personality, individual characters you come to like, a band that forms that you feel/want to be a part of, doing good in the kingdom, it's a fictional place, not a real past, there are different side stories and villains, etc.
It works these similarities and differences in well, retaining some of the best parts of the original and making it its own at the same time, in a way that keeps it interesting. Still very Chinese (lots of makeup, repetition, extreme cheesiness in places...), but a decent one at that.

Both FLs pretend to be eunuchs to stay by the emperor's/king's side. Both MLs have an initially cold personality but are very loving, both FLs are high-spirited.

Both FLs come from the modern day real world into a historical world where they at one point are a servant, and at another pose as a man/are in a man's body. Both MLs are emperors who fall deeply in love with the FL, but realize she must return to the real world.

another time-travel romance drama where a teenage girl travels back in time and falls in love with not a king but a young lord in this one. it is also adorable like this drama and the story is well-written.

Both FLs travel from the modern day to a historical world and fall in love with the ML. Both FLs begin to fade in and out as their time in that world draws to a close.

Parallels between My Devine Emissary and Wonderful Fate include:
The female lead is a student who is struggling academically and is reluctant to take her tests.
She travels back in time and/or into a historical narrative, where she encounters the ML, the emperor.
The connection between the leads in both dramas is that the leads characters are quite similar in that they initially despise one another before becoming friends.

Both FLs are spirited and a bit silly, and enter the palace disguised as eunuchs. The emperor discovers or knows their secret and falls in love with them.