I got my raspberry pi 5 the other day and have it up and running with LE11. 4K HDR with HD audio is working great.
oddly I was unable to install LE12 - I got a Mount_storage error. using the same card and process LE11 worked fine. I tried with 2 different cards and had the same result.
i got the same error trying to run the aarch64 LE12 images. The LE11 ARM64 images booted fine on the RPI5. Out of pure frustration I assumed that the power supply i had been using on my RPI4 would be sufficient for the RPI5. It is not. When i put a 20w PD USB-C supply to the board suddenly the LE12 images booted fine. YMMV but try using a more powerful PS (official recommendation is using the 27w PD USB-C PS)