openSUSE TW, I have everything up-to-date. Using X11. As you can see in the attached screenshots. Some context menus have good icon sizes and reasonable padding, while others are pretty weird.
different font sizes.
From the setting, I already have 11 as a general size for all types of fonts.
This is because you’re using a scale factor larger than 100% on X11 in Plasma 5. With that combination, icons in Plasma context menus will be too small, for unfortunate technical reasons. If you’re interested in them, read through 356446 – [Meta] Enable Qt scaling on X11.
On X11, you can fix this by setting
/etc/environment and rebooting. However as a consequence, mixed-DPI multi-monitor setups will break even worse than they’re already broken on X11.
Alternatively, you can use the Wayland session, where both Plasma context menu icon sizing and mixed-DPI multi-monitor setups work out of the box.
This has fixed the issue. Thankfully I use only one monitor.