How to make Plex use tag info from MP3s

I have a large collection of MP3 albums and have painstakingly added in track info including album art and lyrics. When I imported the library, I checked the box to use existing tags, but it did not import album art from the tag, nor lyrics. How can I make it do this?

Embedded lyrics are not supported.
Only as ‘sidecar’ files.

Embedded artwork can be wonky, but you’ll have a better chance that it’ll get selected as default when you do this:
Settings - Server - Agents - Albums - last.fm
Drag the line ‘Local Media Assets’ into the topmost position.
Repeat the same under
Settings - Server - Agents - Albums - Premium Music