@cbay , you could actually test two leptons by disabling i2c port for one (or both) of them. Lepton starts up streaming data by default via SPI, so you can get frames from it without any communication.
In order to do that, you would need to run two instances of voxl-lepton-server and the second instance would have to be modified to read from a different config file and to not kill the existing voxl-lepton-server process (and probably name itself differently, so that the first server does not kill the second during start-up).
If this all works, then in order to actually test two leptons with i2c communication (which we use the set the FFC mode depending on the flight mode and also reset the sensor if it gets into a weird state while streaming), the lepton server functionality would probably need to be added to a C++ class so that multiple instances could be run from the same process. The reason is that there needs to be a single point where the i2c switcher is set to one or the other lepton, right before communicating to one of the leptons (without the other server / thread creating a race condition and trying to do communicate right at the same time)..
I'd have to think about the fastest way of doing this, but at least you should be able to test two leptons with second not using i2c with very minimal changes.
Here is the source code for the voxl-lepton-server in case you did not already find it: https://gitlab.com/voxl-public/voxl-sdk/services/voxl-lepton-server/-/blob/master/src/
Alex