Abandoned, in favor of Lyrics Plus for Spicetify v2. If you wish, you can still download and use genius-spicetify in Spotify v1.1.58 or older with Spicetify v1.2.1. Otherwise, check out Lyrics Plus, it has more Lyrics providers and customisability.

Spotify desktop client app fetches lyrics from Genius and Musixmatch

0. Make sure spicetify-cli is installed and run spicetify apply normally.
1. Run these commands, one by one:

Linux and MacOS in Bash:

cd "$(dirname "$(spicetify -c)")/CustomApps"
git clone https://github.com/khanhas/genius-spicetify genius

Windows in Powershell:

cd "$(spicetify -c | Split-Path)\CustomApps"
git clone https://github.com/khanhas/genius-spicetify genius

Don't have GIT?, Windows in Powershell:

cd "$(spicetify -c | Split-Path)\CustomApps"
Invoke-WebRequest -Uri https://github.com/khanhas/genius-spicetify/archive/master.zip -UseBasicParsing -OutFile .\genius.zip
Expand-Archive -Path .\genius.zip -DestinationPath .
Rename-Item "genius-spicetify-master" "genius"

3. Finally, run:

spicetify config custom_apps genius
spicetify apply

If you already installed before with those steps above, you just need to run these to update: Linux and MacOS in Bash:

cd "$(dirname "$(spicetify -c)")/CustomApps/genius"
git pull

Windows in Powershell:

cd "$(spicetify -c | Split-Path)\CustomApps\genius"
git pull

I already included a free user token to fetch full and synched lyrics from Musixmatch database. Since Musixmatch has limit rate per token, too many requests with same token will temperory block it from receiving result. Follow these steps to retrieve a personal token:

1. Download and install Musixmatch offical app: https://download-app.musixmatch.com/download Windows user: install it via Windows Store.

2. You don't have to log in!

3. Now in Musixmatch app, hit Ctrl + Shift + i to bring up DevTools.

4. Switch to Network tab. Hit Ctrl + R. Filter results with "apic":

5. Click at any result, it will show up request detail panel. Scroll all the way down. Note down usertoken

For example request above, I should note down:

200501593b603a3fdc5c9b4a696389f6589dd988e5a1cf02dfdce1

6. In genius app folder, open file manifest.json. In that file, look for UserToken, then just fill it in with yours.

7. Restart Spotify and Enjoy!

This app assets were taken from lyrics app from Spotify team and modified by me. I do not own any of these code and they should not be reused anywhere else.