Similar to the feature in iTunes or Apple Music you’re able to add custom lyrics to each and every song! I propose the same ability inside Plex that would work when lyric find isn’t available for that particular song or album or maybe somebody wants to turn off lyric find and just use only custom lyrics they wouldn’t have to necessarily be timed but that would be a cool feature to add later!
There’s already two existing feature suggestions aiming at (a) manually editing/entering Lyrics within Plex and (b) reading embedded lyrics. I suggest you comment/vote in those threads in order to avoid distracting votes/attention.