Issues installing data.table in R 3.6.3 (Oct 2020)

Question

I'm using a Mac with OS Sierra 10.12.5. I'm having trouble with installing the R package "data.table," including if I try to install via install.packages("Hmisc"), or install.packages("data.table"). Both result in:

installing to /Library/Frameworks/R.framework/Versions/3.6/Resources/library/00LOCK-data.table/00new/data.table/libs
** R
** inst
** byte-compile and prepare package for lazy loading
** help
*** installing help indices
** building package indices
** installing vignettes
** testing if installed package can be loaded from temporary location
Error: package or namespace load failed for ‘data.table’ in library.dynam(lib, package, package.lib):
 shared object ‘datatable.so’ not found
Error: loading failed
Execution halted
ERROR: loading failed
* removing ‘/Library/Frameworks/R.framework/Versions/3.6/Resources/library/data.table’

The downloaded source packages are in
    ‘/private/var/folders/bl/lgd7_j2j087f24tcly84xg580000gn/T/RtmpbM5EaD/downloaded_packages’
Warning message:
In install.packages("data.table") :
  installation of package ‘data.table’ had non-zero exit status

I then tried installing directly from the .zip at: https://github.com/Rdatatable/data.table, but got the following "not available for R 3.6.3" message:

> install.packages("~/Downloads/data.table-master.zip")
Warning message:
package ‘~/Downloads/data.table-master.zip’ is not available (for R version 3.6.3) 

I tried the approaches in this thread, but none worked :\ : Problems installing data.table for R

Any advice for what I can try next, or where I can access a version of data.table specifically for R 3.6.3?