Installation instructions fail due to "No matching distribution found for PySide6>=6.4"

[TCPhelps]

Following the instructions exactly, the installation fails as there is no PySide6>=6.4:

(venv) user@machinename:~/projects/external/sushi-gui$ pip install -r requirements.txt
ERROR: Could not find a version that satisfies the requirement PySide6>=6.4 (from -r requirements.txt (line 1)) (from versions: 6.0.0a1.dev1606911628, 6.0.0, 6.0.1, 6.0.2, 6.0.3, 6.0.4, 6.1.0, 6.1.1, 6.1.2, 6.1.3, 6.2.0, 6.2.1, 6.2.2, 6.2.2.1, 6.2.3, 6.2.4)
ERROR: No matching distribution found for PySide6>=6.4 (from -r requirements.txt (line 1))

sushi-gui doesn't appear to be on the elk-os Raspberry pi image, so I'm installing it in Ubuntu on WSL2 in the hopes that I can connect to the Pi remotely.