Icon themes for GIMP (Should be compatible with 2.10 and above)
(in 2.99 uncheck Use symbolic icons if available in Preferences -> Icon Theme)
How to install:
Launch GIMP and go to Edit > Preferences > Folders > Icon Themes and see where it looks for the icons, put the custom icon theme in that folder.
Alternatively, click the button "Add a new folder" and give it a new path to search for the custom icon theme(s). (needs restart)
There must a hicolor folder with an index.theme file in it (you can just manualy create those and index.theme can be empty) on the same path as the custom icon pack
Blender
Download
Download through download-directory.github.io (very slow): here
Blender Symbolic
Download
Download through download-directory.github.io (very slow): here