[2023] Problem with Leader

Right-click on stellaris.exe, properties, compatibility. Tick "disable fullscreen optimizations" untick every other box in that dialog, Apply, and exit.
Then in the launcher Game Settings menu, select the fullScreen display mode, Vsync off, refresh rate 60

If that doesn't help:
DXDIAG is a program you run from the Windows search box on the task bar. After running it will open a window and start collecting info with a progress bar in the lower-left corner. When it completes click the 'save all information' button and save it to a file then attach that file here.

Please attach here your Documents/Paradox Interactive/Stellaris/settings.txt and pdx_settings.txt .
From your Documents/Paradox Interactive/Stellaris/logs/ folder, attach here system.log , error.log .  

You say you don't use mods but there's a mod error in that log - are you 100% sure they are all disabled in the launcher?

Alicebis said: I tried everything from dx9 to dx12 and it didn't solve the issue.

Those logs show DX9 in use. The game does not use DX12 (so I don't know how you could have tried that?), but we should try DX11.
In your Steam Library right-click on this game and choose Properties. In the Launch Options line, paste this in there:
-dx11

If that doesn't change anything, I can only guess this is a bug. Do you have access to any other computer to test this on?  

I see we are back in borderless windowed mode - I take it that settings does not affect the problem?

There is a slightly newer nVidia driver now, may as well try that

Download the latest official NVIDIA drivers

Download the latest official NVIDIA drivers www.nvidia.com
If those don't help, as I say I guess this is a bug. Make a new thread in Bug Reports, and attach there a short movie of what you are seeing happen in the game, and describe there for QA what game choices you need to make to trigger the problem.

Sorry about that!