Hey BearDuckXD!
Indeed, you can dupe items on a 1.16.5 server using the book dupe method. However, Wurst for Minecraft 1.19.4 won't work for that since it doesn't include the required .dupe command. You'll need a version of Wurst made for Minecraft 1.16.3 - 1.17(.0). I'd recommend using Wurst for Minecraft 1.16.5 in this case.
It's important to note that this is all assuming that the server you're referring to hasn't patched the book dupe with third-party software or plugins. You'll want to pay close attention to the compatibility section on the Wurst Wiki page.
Hope this helps!
