Iris Raycasting Trouble

I'm trying to use Iris in a datapack I'm working on but I'm having trouble with IrisDataGen. I went through all the steps in the readme but I keep getting errors regardless of what version I to run it for. I tried using 1.21.10 and 1.20.4 (which is the version used in the documentation) for the version args but it doesn't work. Is Iris still supported, or is there a better alternative?
Here are the errors I'm getting:
Version = 1.20.4
"[+] Downloading official obfuscated jar client archive and mappings"
A subdirectory or file downloaded already exists.
The syntax of the command is incorrect.
The syntax of the command is incorrect.
[+] Fetching version 1.20.4 from https://piston-meta.mojang.com/v1/packages/63ce9f1ec1b2256e9112790dd6f9d4ee1b0ff352/1.20.4.json
[+] Downloading client.jar for version 1.20.4
[-] Could not write to file ([Errno 2] No such file or directory: './downloaded/1.20.4//client.jar')
[+] Downloading client.txt mappings for version 1.20.4
[-] Could not write to file ([Errno 2] No such file or directory: './downloaded/1.20.4//client.txt')
[+] Downloading Minecraft Java libraries for version 1.20.4
(1/88) java-objc-bridge-1.1.jar
[-] Could not write to file ([Errno 2] No such file or directory: 'build/1.20.4//java-objc-bridge-1.1.jar')```

It errors out for all 88 steps.

I haven't been able to find anything online about this, am I doing something wrong?