Cannot set global scale to 100%

Hi,

It seems I cannot have a global scale of 100%.
When I set it to 100%, some apps, in particular browsers, behave like it is set to 106.5% i.e., a 100px square takes 106px on screen.

If I set it to 106.5% or 200%, the scale is correct i.e., a 100px square takes respectively 106px and 200px.

I’m on Ubuntu 22.04 and using plasma 5.27.11

Any clues about the issue or where to start looking?