For a much more general solution (since NetEase Music is only a Chinese Music Service Provider, I don't think other language is provided), probably need integration of popular translation APIs, which if user want to use the translation feature needs to enter their API in the settings. If the API is given, then it could be adapted to translate to the language selected by the user.
For the Romaji part, I found a library called WanaKana or Kuroshiro, is precisely a convertor for Japanese to Romaji and other notations. There could be two buttons on the lyrics page meaning enable/disable light/dark translation and romaji.
What do you want to be added?
Lyrics Translation and Romaji (Phonetic symbol for Japanese songs)
Additional context
Some trivia thought I could think of:
Reference
Is this a server-specific feature? (e.g. Jellyfin only)