Works on Paper 1.21 with zero issues. The only thing is the items are outdated so I used the help of chatgbt to list me all the items available in 1.21. After that, the plugin worked and is seriously a GAME CHANGER in a great way! Unique and I love what you're doing! Please keep this evolving as you do your other plugins.
A major suggestion, which would work great for quests and stuff, is to add a way for players to get "stonger" or have a higher weight limit via permissions or different config files. This would allow us to reward players with extra weight limits which I think would be a homerun! Start folks off slow, and they finish quests (or something) and by the end-game they can carry quite a bit more.
Thanks for the review and suggestion. Only saw it now, the custom max weights were added in v1.5.
And yes the item names in the config should be outdated, for future reference and for anyone else that needs it, you can check for current item names here:
https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/Material.html