I noticed that there was another lifesteal smp plugin but it wasn't compatible with latest versions.
Here Is one I found on spigot, I don't know if it works cause i haven't tested it yet but feel free to check it out mods, I know I'm not the only one that wants this.
You need 1.17.1 Paper to run it properly.
Let me know if this is added.
Link: https://www.spigotmc.org/resources/lifesteal-smp-plugin.94387/