You can almost so this with the solar kit.
If you have a generator, you probably have a transfer switch. Power the Sense from a circuit fed from the transfer switch. (Don’t power the Sense from a UPS).
Use the main current sensors on the utility power feed, and the “solar” current sensors on the feed from your generator.
When your house is on Utility power, Sense will work normally, and show zero “solar usage”.
If utility power goes away, the sense powers off, but will restart when the generator kicks in. The app will show that all power is coming from “Solar”.
Other than a short outage during the transition, this works very well if all loads are on the transfer switch.
If only some loads are protected, you will have some reporting issues if the utility power comes back, and the transfer switch waits a few minutes before returning the protected loads to utility power. During this period, some loads are on utility power, and some are on generator power. It is probably that the two are not in perfect phase sync with each other, and that the phase difference will be drifting. Sense doesn’t deal with the two sources being out of sync and will show slowly varying values for utility power usage that range from correct, to completely wrong. If the actual utility usage is 1KW, Sense will show values that range from 1KW to -1KW (negative one KW).