You don’t have a Debian installation, you have Raspberry Pi OS (formerly Raspbian) which is a derivative of Debian. Home Assistant Supervised is officially supported exclusively on Debian and not on any other distro of Linux, not even derivatives of Debian. This is all clearly explained in the installation instructions for Home Assistant Supervised.
You are, of course, free to install it on Raspberry Pi OS but the result will be an unsupported system (it will indicate this in Settings > System > Repairs). What does “unsupported” mean? It means you cannot receive support from the development team (i.e. in GitHub) for any problems that may arise with your system. Your source of assistance is limited to community forum(s).
In addition, the requirements for Home Assistant Supervised evolve over time. The requirements and associated installation script only take Debian into account and no other Linux distro. In fact, recent versions of the installation script refuse to work with non-Debian systems so you’re obliged to perform its tasks manually. This makes adapting your unsupported system, to meet the latest requirements, just that much more challenging.
Now that you know the consequences, you can make an informed decision about how you wish to proceed.