(With PPSSPP anyway, not antimicro)
I built PPSSPP from ports and did a
make config to enable the OLDJOY build option. After building and installing that version, my joypad works under fine under PPSSPP without any configuration under TrueOS or PPSSPP.
The controllermap package/port includes testjoystick and testgamepad but it doesn’t fake keyboard input too like antimicro claims it can and I had no luck getting its (or anitmicros) SDL2 controller string working with PPSSPP.