Slimefun4 not working on aternos spiggot 1.21

[wartuki]

❗ Checklist

• [X] I am using the official english version of Slimefun and did not modify the jar.
• [X] I am using an up to date "DEV" (not "RC") version of Slimefun.
• [X] I am aware that issues related to Slimefun addons need to be reported on their bug trackers and not here.
• [X] I searched for similar open issues and could not find an existing bug report on this.

📍 Description

when i tried using any of the items like the backpack it would just place and not open and the book didnt work nothing work so i tried commands and everytime i got an error and i tried reinstalling but that did nothing

📑 Reproduction Steps

1 have aternos spiggot 1.21 2 have slimefun4 [1448] installed 3 try using any commands/item

💡 Expected Behavior

a fixed version so i can play in 1.21

📷 Screenshots / Videos

i dont think thats supposed to happen

📜 Server Log

An internal error occured while attempting to perform this command

📂 /error-reports/ folder

No response

💻 Server Software

Spigot

🎮 Minecraft Version

1.20.x

⭐ Slimefun version

Slimefun4 1448

🧭 Other plugins

No response

[Boomer-1]

slimefun does not support 1.21 yet. we're waiting on an issue with spigot to be resolved for 1.20.5. once that is done, we will have a 1.21 version.