This plugin isn't really plug'n'play, however the installation is still pretty simple:

YOU CAN SKIP THE FOLLOWING 5 STEPS IF YOU ALREADY USE PAPERMC SERVER

1. Download PaperMC https://papermc.io/downloads/paper 1.21+ if you haven't alread
2. Create a folder and insert the downloaded .jar file into it
3. Create a file called "run.bat" and insert following content into it: java -Xmx1G -jar <filename of the file you downloaded file>.jar nogui
4. Run run.bat, wait for a while until it says done or similar then close the window
5. Open file called eula.txt and change it's content from eula=false to eula=true
6. Download the latest full version of the plugin and insert it into the newly created folder called "plugins"
7. Open server.properties file and change the following content from
   require-resource-pack=false
   resource-pack=
   resource-pack-id=
   resource-pack-prompt=
   resource-pack-sha1=
   to
   require-resource-pack=true
   resource-pack=https\://github.com/DRKocourek/NyanCatDeath/raw/refs/heads/main/NyanCatSoundEffect.zip
   resource-pack-id=
   resource-pack-prompt=The resource pack is needed for a special death sound effect via a server plugin ({"text"\:"More info here","color"\:"\#00ff8d","clickEvent"\:{"action"\:"open_url","value"\:"https\://github.com/DRKocourek/NyanCatDeath"}})
   resource-pack-sha1=dc6332d1811b20407a0c1c3c514376b7516a812c
8. Then just start the run.bat file again start Minecraft 1.21.4 and connect to server with address localhost and if everything works properly you should be able to hear the nyan cat on death )