Modifying the firmware of a latest-generation Xiaomi phone to enable call recording in a way that ensures clear and comprehensible voices without the other party noticing the recording

I live in Italy, where it is legally allowed to record phone calls. This feature is essential for me because I use my phone for work and I'm often away from the office. Therefore, it's easier for me to take notes or quickly mark the date and time of an appointment by recording the call. Unfortunately, in recent versions of Android, this capability has been removed, or if it is allowed, it requires an audible notification or sound to alert the other party that they are being recorded. This operating mode is not acceptable to me because even though my intentions are good, clients immediately become uncomfortable upon hearing such a warning, and I want to avoid this. There are dozens of apps available for Android that claim to record phone calls, but unfortunately, the ones I have tried, including the most popular ones, do not work effectively. Ideally, I would like to revert to the old Android 8 phone, which had native call recording functionality already enabled from the moment of purchase. I would like someone to modify a new Xiaomi phone that I need to buy to enable me to do the same thing. Alternatively, it is also acceptable to install external apps as long as we can be certain that they work well, record voices clearly, and do not notify the other party of the recording with any sound or alert