Porting/Briar
It is possible to build Briar from source for POWER (tested on Debian Bullseye for ppc64le). To do this, follow the Directly from source instructions for Briar-GTK. When building Briar Headless, you'll need to follow the additional instructions from the "To get Briar running on ARM devices" section of Using Briar GTK at a distance. The patch no longer applies cleanly, but it's trivial and obvious how to resolve the conflict.