Multiplayer modding is still very much alive and well. There is both the client-side route (where everyone uses a modpack tool like https://atlauncher.com/ http

Multiplayer modding is still very much alive and well. There is both the client-side route (where everyone uses a modpack tool like https://atlauncher.com/ https://atlauncher.com/) or the successor to Bukkit, Spigot (and its High-performance fork, PaperMC: https://papermc.io/ https://papermc.io/) Spigot/Paper are bukkit-compatible and you can load modpacks from the spigot.org site, or even bukkit.org, which is still operational to this day. Source: I run several instances myself and I help develop a server management tool for it: https://craftycontrol.com/ https://craftycontrol.com/