Unable to install on macOS Catalina

While trying to install on macOS Catalina, I get the following error:

Error: package or namespace load failed for ‘rstanarm’ in .doLoadActions(where, attach):
 error in load action .__A__.1 for package rstanarm: is(module, "character"): object 'm' not found
Error: loading failed
Execution halted
ERROR: loading failed
* removing ‘/Library/Frameworks/R.framework/Versions/3.6/Resources/library/rstanarm’

This is my session info:

R version 3.6.2 (2019-12-12)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: macOS Catalina 10.15.3

Matrix products: default
BLAS:   /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
LAPACK: /Library/Frameworks/R.framework/Versions/3.6/Resources/lib/libRlapack.dylib

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

loaded via a namespace (and not attached):
[1] compiler_3.6.2 tools_3.6.2   

I am quite clueless on how to proceed further.

No source file or test is named. Start by reproducing the installation on R 3.6.2 and macOS Catalina using the supplied session information, then inspect the package installation and namespace-loading failure. Done means rstanarm installs and loads without the reported error.