There is a lot of historical information on your website, about config.txt changes required to get your DACs to work, some of this is likely to be outdated, spreading over many years of posts and Linux kernel versions.
It would seem good company practice to have an authoritative (and simple?) install guide distilling this information, kept updated with operating system releases, organised by hardware (RPI 5, 4, etc) and operating system & version, rather than have this information spread over blogs and support requests, and wider internet searches.
This guide should be easily found from your homepage.
I purchased the DAC2 HD on 13/07/2020 and this has been a continual problem in using your hardware. Making no explicit support for operating systems which are widely used on Raspberry PI (such as Ubuntu) is also not appreciated. Maybe your website should have warnings 'DO NOT buy our products if you don't intend to use PI OS / HiFiBerry OS'
I have spent a day trying to get what is an up to date hardware and OS combination working with the DAC2 HD with no success today (RPI 5, PI OS Bookworm) and also Ubuntu 24.04. Neither successful, I have been around many corners of the internet, and your website.
Linux 6.6.28+rpt-rpi-2712 #1 SMP PREEMPT Debian 1:6.6.28-1+rpt1 (2024-04-22) aarch64 GNU/Linux
On this basis I could not recommend anybody to buy a HiFi Berry / Modul 9 product. This is what one expects of buying products from AliExpress not Swiss companies, where things should run like clockwork and be user friendly.