After upgrading my Linux KDE system to plasma 5.22, SMART Status gave me this warning:

"SSD 256GB (/dev/sda)
The SMART firmware is not reporting a failure, but there are early signs of malfunction. This might not point at imminent device failure but requires longer term analysis. Back up your data and contact the manufacturer of the disk, or replace it preemptively just to be save."

The device error log contains records of errors.

After inspecting my SSD, I found no error on it. Is this a bug?

I very much doubt Plasma upgrades have anything to do with this, as it is GUI system that does not interact with SMART at all.

I moved your post to the Linux section, as it is not KDE or Plasma related