This theme Yaru-geel-W-plus is a variation on the suru-plus icon theme https://github.com/gusbemacbe/suru-plus . I made a lot of changes over time. To much to remember. The theme is packed as tar.zst that was by far the most compact method. I use a lot of KDE and also often Ubuntu. I put some work in making the theme fit in both environments.

For KDE you could open the konsole (e,g in Dolphin with F4 of Shift-F4) in the folder where the file is located and say:
tar -xf Yaru-geel-W-Plus.tar.zst -C ~/.local/share/icons/
For e.g. Ubuntu this could be:
tar -xf Yaru-geel-W-Plus.tar.zst -C ~/.icons and then choose icon theme using gnome-tweaks.
There are four images on top of this item: first two Plasma (one desktop with Dolphin, the other menu) second two Ubuntu (desktop with Gnome-files, the other one menu)