Thanks for the guide. After much web searching and frustrating attempts, finally got a Rasp Pi 5 up and running with Bookworm OS, Squeezelite and an Allo Boss DAC hat. The Pi5 has issues with I2S so the overlay I used in the end was:
dtoverlay=allo-boss-dac-pcm512x-audio,slave

The last bit forces the DAC into slave mode rather than master mode.

I have an LMS set up on a Pi4 and that managed to find the Pi5 as a player. Happy listening.
Cheers - Julian