Is it possible to connect to BTCPay server remote c-lightning node? I have BTCPay server and would like to use external c-lightning node which i have funded and prefer more over BTCPay server local docker container (DC). 

In store configuration i see that there is option to connect to c-lightning over tcp or unix socket (this one is used when i connect internal node because c-lightning DC socket is linked to BTCPay directly).



How can i connect over TCP? As i uderstand this is not public nodes port (9735) which is used to communicate between nodes but some API port? How can i enable it on c-lightning? Is data sent plain and i should secure communication (lan, fw, vpn etc.)?
Port 9735 is the lightning port. What BTCPay wants is the API.
C-Lightning does not support TCP natively, but one can use socat as I did in the docker entrypoint to bridge unix to TCP.