With the package natively compiled soon after. Some effort is made into porting the GNU Fortran compiler, gfortran, to Apple's take on ARM's architecture (proposed for the summer 2022, GNU Compiler Collection, v12.#, though experimental support is available in a V11 fork). Followed by a tweak to the dependency list for Apple silicon builds of RStudio, to convert the offending modules to C, before natively compiling. The like of GNU's f2c need to be tweaked to support the FORTRAN 90 standard, by adding some non trivial logic to handle the intrinsics added between the 77 and 90 standards, the other changes are relatively trivial. There is an ancient, and free GNU tool, f2c, that converts FORTRAN source to C, but it only supports the FORTRAN 66 and 77 standards.

The issue being there isn't a native, stable, open source, Apple Silicon compiler for FORTRAN 90, though there are commercial compilers, sold by NAG and ARM. RStudio is written in a mix of languages, that annoyingly includes some FORTRAN 90.

Download rstudio for mac m1