Hey Paul,
Thank you for your reply. I successfully managed to install from the local copy without further problems.
With respect to the R installation, should I also save e.g. the @add_rcran_ubuntu_18.04.tgz in the same directory to install the corresponding R dependencies for the AFNI version I installed now, or are there no variations over time?
Also, thank you for your suggestion, this is probably good practice in the interest of computational reproducibility anyway.
Best wishes,
Stef