Duplicate of this. Won’t be added since it would require a change in the Symfonium content declaration on Play Store according to Tolriq.
In addition to the tools Tolriq mentioned in his reply (MusicBee, Lyrics finder) you should take a look at lrcget, which can automatically fetch lyrics in bulk from lrclib.
However I’m personally not a friend of auto fetching lyrics. The majority of the results (for me) was either inaccurate or outright wrong.