After having problem with adwaita-icon-them-3.24.0, (reported in other bug)
I decided to give a try by removing gnome service from the
list of "meta-package" to install.
So in fact keeping 'only' XFCE.
I tried two times, once after the adwaita problem, the other after a reboot
and from scratch (except partitioning).
The result was the same (from poorly taken notes):
warning: collision encountered:
warning: arbitrarily choosing 7qnfb...icons/hicolor/icons-theme.cache
In unknown file
That's it, what I had noted.
So, I had to boot with an other system to report this, was unable to get
guix-sd 0.13.0 usb install 32b to install.