As explained on the simple funds overview plugin you just have to start lightningd with the plugin argument like this:
of course plugins could also be written in other languages than python.
You see this mechanism also in action in this video which explains who to write and run your own ...
As pointed out in similar questions backups are tricky with lightning. In the case of lightning each payment channel is a 2 of 2 multisig wallet. One of the keys is in your possession and it differs for each channel but in generally is derived from your master key.
The masterkey in c Lightning is 32 byte and stored in binary in ./lightning/hsm_secret
It would appear that you have (or rather had them at the time you ran the commands) 6 channels that were funded, but not yet announced. This is most likely why your node sees them (getinfo) but gossipd doesn't yet (listchannels) since they haven't been announced just yet.
as Rene Pickhardt pointed me:
without context I studiert you installed the pylifhtning client via
pip and upgraded you lightning node later so that the APIs have
different versions. But that is only a wild guess for a common error