The new Xfce 4.16 release changed the icon name scheme. It now follows the freedesktop.org naming specification. Gnome did something similar.
For example, the name of the Thunar icon changed form "Thunar" to "org.xfce.thunar" . This is just an example, since (nearly?) all icon names changed. I did not find a list of all changed icon names.
If possible, please update the delft icon theme to match as many as possible.
The new Xfce 4.16 release changed the icon name scheme. It now follows the freedesktop.org naming specification. Gnome did something similar.
For example, the name of the Thunar icon changed form "Thunar" to "org.xfce.thunar" . This is just an example, since (nearly?) all icon names changed. I did not find a list of all changed icon names.
If possible, please update the delft icon theme to match as many as possible.
https://xfce.org/about/news/?post=1608595200 Example commit for Thunar https://gitlab.xfce.org/xfce/thunar/-/commit/78f73f668c090e590b6492ed9be781e2907b4db6#2436625087020069e8e80f81234011a6e30ed847