Can a 21.5 inch iMac (non-Retina late 2015 - 2.8 Ghz, Intel Iris Pro graphics, model 16,2) drive two external displays?
Not according to EveryMac who are usually spot on with their info, including unsupported 'hacks', none of which are mentioned for this model.


  This model can simultaneously support the internal display at full native resolution and up to 4096x2304 on an external display in both extended desktop (second workspace) and video mirroring (internal display duplicated on the external display) modes.