@jk996 _ I've seen Rule The World. The series is a mixture of Scarlet Heart (harem in reverse, several princes fight for the throne) and fantasy (he who gets the female lead gets the power to rule the world). Can't remember a time travel plot.
@Naiwen _ your comment on a FL going to a fantasy, gaming, webtoon, manga, comic or book universe made me think of:
LET's shake it 1+2 : an ET-like warrior out of space lands into the body of a lady in ancient China. To make matters worse, he/she develops feelings for his/her supposed brother.
Mengfei Comes Across (2018): has the look and feel of series like Oh My Emperor and Go Princess Go, but it lacks the time travel plot. Modern elements are blended into the story.
Meet Me @1006 (2018) is more time manipulation than traveling, but still a good story. A female reporter and male lawyer from different time areas are able to see each other. They decide to work together meeting each day at 10:06
I know you prefer time travel and harem-in-reverse put together...but how about just one good looking guy who's good to one lady and her child? I find A Boy and His Samurai (2010) such a sweet and cute movie!
Second, the time travel productions in 2019 and beyond. Can't say much about them, just mentioning:
Spring Flower, Autumn Moon (2019) this one has the same actress as Oh My Emperor. Trailer: https://youtu.be/W3yriR5Aibg
Dreaming Back to the Qing Dynasty (2019) with the actress from My Huckleberry Friends. No footage available, but the synopsis from the novel sounds interesting:
A girl living in the 21st century, lost her way in the Forbidden City, unexpectedly travelled through time to the Qing Dynasty. She also involuntarily embroiled in the dangerous politics within the imperial palace. The passionate and fiery 13th prince, the reserved and introverted 4th prince, the young sister whose fate was full of trouble and misfortune, the majestic Emperor Kangxi, countless characters who you’ve read in the history books, with their respective 4 types of human emotions being happiness, anger, sorrow and joy, coming thick and fast.