Well, then thanks for reporting the issue to the RPi devs 
.
And we learned that 64bit RaspiOS is shipped with kernel 5.10 now 
And I found our great that this kernel package now contains the 64-bit kernel only, reducing the obsolete overhead and disk usage + writes for the three 32-bit kernels . I hope the same will be done for the 32-bit 5.10 kernel package once released, so that no 64-bit kernel is included by default.
a fix is available on Kernel 5.10.9-v8+, available via rpi-update
https://www.raspberrypi.org/documentation/raspbian/applications/rpi-update.md
root@DietPi3:~# uname -a
Linux DietPi3 5.10.9-v8+ #1396 SMP PREEMPT Thu Jan 21 16:01:58 GMT 2021 aarch64 GNU/Linux
root@DietPi3:~# cat /sys/class/thermal/thermal_zone0/temp
46160
root@DietPi3:~#
Just did a system update. Temp is back!!
Thank you all for your time and troubleshooting this.
The Pandemic has me broke right now but as soon as times are good again I will be sending a donation. Love the work being done on this dietpi system. Saves me a lot of time setting up systems. Solid!
Thanks again!
i did put in this my dietpii “sudo rpi-update” and I got this “sudo: rpi-update: command not found”
did you install rpi-update before?
apt install rpi-update
But keep in mind, rpi-update will bump you to next kernel branch, which is even more beta 
nope, I have no idea how linux works I just copy and paste commands with some understanding on how it works.
I will just wait for the official release then, a working system is better than a beta system.
thanks
well you are using Raspberry OS 64bit. This is already Beta 
Hi guys,
kernel 5.10.11-v8+ has been released by RPi Foundation for 32bit as well as 64bit officially