Mmh, this is definitely not Inkscape's standard theme.
Now you'd need to figure out where the icons come from.
So you do not have ~/.config/inkscape/icons ?
Look into the files in /usr/share/inkscape/icons - how do the icons in 'icons.svg' look?
Or did you install the Inkscape flatpak? (if so, you can also update to 0.92.3)
If nothing helps, you could do a full text search in any svg files on your disk, for some of the icon names that are unique to Inkscape, like the mesh gradient tool icon (find its id in the icons.svg file in /usr/share/inkscape/icons).