Just tried with a Pi 5 / Bookworm - this sequence got things lighting up for me:
First I enabled SPI in sudo raspi-config and rebooted.
Then I created a virtual environment:
python -m venv --system-site-packages ~/.virtualenvs/pimoroni
and activated it:
source ~/.virtualenvs/pimoroni/bin/activate
Then I installed the UHHD library and supporting packages using pip:
pip install unicornhathd spidev numpy
Then I downloaded the examples from Github, navigated to them and ran them thus:
git clone https://github.com/pimoroni/unicorn-hat-hd
cd unicorn-hat-hd/examples
python demo.py
The examples run really fast on a Pi 5 :D