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Do you have GPU scaling turned on in your global GPU settings?
Kassoulord: Thank you for your reply :)

I checked that indeed, and it was not configured properly.
For users who may have the same issue that I had, I use a laptop with 2 GPUs : an Intel HD renderer, and an Nvidia GPU.

I had to change the setting of the Intel renderer, right-clicking on the desktop, to choose the IntelHD Integrated peripheral configuration panel. Then, in Display, I changed the desktop scale type to Stretch to full-screen, applied the settings and everything works perfectly now :)

I attached a screenshot (in French though) to show where to pick the right choice.
Glad I could help! :)