Since the "fix" usually requires a fresh installation file because the old links are dead, users must look elsewhere.
If you are looking for a fix for a version (a newer, less common fork): eaglercraft 120 1 fix
Some 1.20 ports require specific "Eaglercraft 1.20" servers. You cannot join standard Java 1.20 servers unless they have a specialized plugin (like EaglercraftXB) installed. Since the "fix" usually requires a fresh installation