When using this application style, some of the icons related to UI actions look jagged. This does not happen with Breeze or other themes. I am not familiar with the way application styles affect these, but I'm guessing that because the icons come from a separate icon theme, it has to do with some Antialias applied by Darkly. For reference, see images (Some are in 4K resolution, some in 1080p to make it more obvious).

I am using Arch Linux / latest plasma version / Wayland and have an Nvidia GPU. This also happens in a separate EndeavorOS virtual machine with a clean config.

1080p:

Same in 4k, slightly less obvious but still noticeable:

Here is how it looks with Breeze, where anti-aliasing seems to be applied: