In the update that I did today Icecat is no longer Deterministic.
I compiled Icecat since there doesn't seem to be any substitutes. After the second time it wrote an error that the two builds were not the same.
My system is this:
Generation 13 Jun 25 2020 16:46:39 (current)
guix d1a26be
branch: master
commit: d1a26bedcc63362609604ec36c7a5ebee825d140
Marinus