My configuration just seems to be about one version ahead and clang one behind. Difficult to tell if this makes any difference, could be worth a try. What I could think of is to try and install it from the local R version (without RStudio) as a package. Or try other suggestions that have been made in the various threads.
system(“gcc --version”)
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/4.2.1
Apple clang version 11.0.0 (clang-1100.0.33.16)
Target: x86_64-apple-darwin19.5.0