Hello, thanks for the prompt answer. Unfortunately disabling the hardware graphics acceleration did not improve the situation ant the text is still blurry as before (please note that after the setting change I also closed and reopened OneNote).
The situation is that is the text is "crystal clear" on the FHD display of the notebook and is blurry when I extend the view on a second monitor that has a resolution of 1600 x 900 px.
To solve this issue, that is common also to other applications, I checked "Disable display scaling on high DPI settings" in the "Compatibility" tab of the "Properties" windows of such application executable files. This fixed the issue in the other applications
and they now appear "crystal clear" also on the second monitor.
The problem with OneNote is that the compatibility tab is not present.