I checked the CRAN results for a number of Rstan dependent packages and all do ERROR for the platforms
r-devel-linux-x86_64-debian-clang + r-devel-linux-x86_64-debian-gcc
which is essentially a Debian 9.21 with gcc 9.2.1 / clang 9.0.0.
Can we ignore this? Anyone an idea on this? The packages I checked are my own (RBesT, OncoBayes2), Rstan & rstanarm … probably the others are also affected.