If I install openmotif with Homebrew as recommended in the documentation (https://amrex-codes.github.io/amrex/docs_html/Visualization.html#building-amrvis-on-macos), I get a compile error when trying to build Amrvis.

This is because XQuartz 2.8.0+ has removed X11/extensions/Print.h (see here: XQuartz/XQuartz#131).

Unfortunately, XQuartz 2.8.0 and newer are the only versions that run on ARM-based Macs, so it does not appear possible to build Amrvis on ARM-based Macs, unless there is a way to install Openmotif without requiring the Print.h header.