sensors command doesn’t show CPU temperature if you have Linux kernel 5.9.0-4. It is common problem of new hardware. But you can compile Linux kernel 5.10.0-rc6 where is the support for reading temperature in procesor AMD Ryzen 9 5900x.

Just add new repository for experimental Debian in /etc/apt/sources.list:

deb http://deb.debian.org/debian experimental main

and install:

sudo apt update && sudo apt install linux-image-5.10.0-rc6-amd64