One of the crates bracket-lib depends on updated and now requires that FreeType be installed on Linux. You can install it with sudo apt-get install libfreetype-dev.
Thanks for the response - I got there in the end:
installed cmake, fontconfig, fontconfig-config.which may have been installed already…but left no fontconfig.ps in the relevant dir
so I then installed:
apt-file, (which led me to ensure PKG_CONFIG_PATH was set, and install…) libfontconfig1-dev
and libfreetype-dev