The last currently available XQuartz build is from 2016, and the X11 libs that it comes with, are outdated as well. Whenever there is a need to link a library with both X11 libs and the libraries from homebrew, a conflict is possible. This is why homebrew usually is focused on non-X11 projects, although there are many that are either only X11-based or don't create such conflicts.
Enter font shaping with harfbuzz and font display with libXft. Harfbuzz is a modern library that has a freetype2 backend, which is both shipped with XQuartz and homebrew. libXft is a respectable core library for drawing, among others, freetype2 fonts, and comes with XQuartz only. Linking both in one program is impossible, because XQuartz's freetype and homebrew's freetype are of different versions and are binary incompatible.
Here is my attempt to resolve the problem. This is a tap that installs libXft (and potentially others) into homebrew-specific locations, built with homebrew freetype and fontconfig, however with a dynamic dependency on XQuartz libX11 and libXrender. Install it with
brew install dk/x11/xorg-macros
brew install dk/x11/libxft
Beware, it is rather hacky and might not build because this is my first ever homebrew formula.
Dmitry Karasik