Because Eaglercraft exists in a legal gray area (it uses Mojang assets but no official code), you won't find it on the official Minecraft launcher. Here is the safe way to access the updated 1.20 version.
Ready to play? Here is your cheat sheet for Eaglercraft 1.2.0 updated: eaglercraft 120 updated
Do not let a restrictive firewall stop your creativity. Eaglercraft 1.2.0 updated is proof that the Minecraft community will always find a way to play—free, fast, and entirely in your browser. Because Eaglercraft exists in a legal gray area
Have you found a bug in the new 1.2.0 update? Join the official Discord communities dedicated to Eaglercraft development (linked via the GitHub page) to report it and help improve the build. Do not let a restrictive firewall stop your creativity
You need a WebSocket server (not a normal MC server).
Let's address the elephant in the room.