One and Only (2021)

Both are historical dramas with the leads trapped between forbidden love and the schemes/politics of the court. Both have a palace setting, a creepy dowager empress who preys on much younger men, and an obsessed SML who wants both the throne and the FL. UL ends happily, OAO ends tragically.

Both dramas have a younger woman and a more older male mentor. In both, the romance is forbidden, ill-fated and is full of yearning.

The Rise of Phoenixes however is beautifully produced, has wonderfully complex and interesting politics. It's also romance at a distance but has lots more quality interactions between the male and female leads.