What do you want the Arduino to do with the audio? Your post isn't clear on this. If it's only switching the output between either of the inputs, any Arduino will do together with perhaps some CMOS switches or a couple of relays.
If you want to use the Arduino as a DSP, you're (1) looking at the higher end range, so forget about Uno's, Nano's and I severely doubt you'd get far with a Nano Every either, and (2) you're in the deep end of embedded systems design if you are serious about DSP applications.
Also, what kind of input/output signals do you envision? You mention 441.kHz which suggests digital. Are we talking SP/DIF here or something like that? Or do you want to stream audio over USB? In case of the latter, I don't think any Arduino is suitable as you'll need a microcontroller that identifies as a USB sound device with the host computer - I think the STM32F4xxx series would be a candidate. But although those can be 'Arduino-ed', it is again another complication on top of your already challenging task.
So let's hear what you actually want to do with those sound input & outputs, because this is going to make the difference between "you might get it done" and "prepare for 10+ years of studying, experimenting & building knowledge" (no offense, but your post makes it clear you have virtually zero experience in embedded systems).