Removing the (nowadays more or less obsolete) Lyrics3 tags from MP3 files still seems an issue in 2019.
Although they can be cleanly removed using Mp3tag by setting your tagging options correctly, removing all tags and immediately doing an Undo, this can be a little scary for some, especially if you have real large libraries (mine is about 150,000 tracks in total). (Personally, I never had problems with this method, kudos to Florian for a great software!)
This is why I wrote a little Python tool to remove Lyrics3 and Lyrics3v2 tags from MP3 files, called rmlyrics3. It also has a "dry-run" option so you can check before actually modifying your valuable files.
The little tool is free and open source software and available on GitHub:
For those interested, there’s also some more technical documentation there.