Yes! If you have a dual sided powermeter you can use either the left or right (or both) powermeters individually as a single-sided powermeter. All you need to do is unpair/unlink the powermeters in the 4iiii App and then only connect the relevant powermeter to your cycling app or computer. Section 3.3 of the relevant 4iiii App User Guide below will walk you though how to unpair the powermeters:
4iiii Android App – User Guide
After a dual powermeter has been unpaired, each powermeter will automatically double your power output to give you total power.