Because this is being adapted from a BL novel but since it's not allowed to show gay relationships in Chinese dramas, they have to censor the romance between the main leads.
No bl, really only bromance (brotherhood). Enjoy watching it's beautiful
Well, I wouldn't consider it bromance either. The series was based on a BL novel but because of the censorship laws in China, they had to tone down the relationship between the two male leads. Even if there isn't anything explicit between them, it's almost impossible to not see how much they care for each other. They have a very strong and special bond, so even the term best friends is not enough to describe their relationship.
Is this based on the movie Farewell my Concubine, or a different story entirely?
This was based on a novel and the author got inspired by Farewell My Concubine to write it. Since both the novel and the movie focus on Peking Opera, some elements are similar, but the stories are very different.
Well, it was based on a BL novel, but because of the censorship in China, they had to tone it down. But, believe me, the relationship between the two main male characters is very deep and sweet. They have called each other "soulmate" several times. Furthermore, I would consider their relationship as more than a simple friendship or brotherhood. You can clearly see how much they care about each other.
https://www.youtube.com/playlist?list=PLhnjbkseqMESllMS8boGw0GVR-aiAVIvA
As far as I know, the novel ends pretty much the same as the drama.