I was wondering if it is possible to connecting two Arduino boards with each other (Uno + Nano) using an ESP8266 mod on one of them and an nRF24L01 on the other board?
I have seen lots of details of connecting two nRF but couldn't find any about ESP talking to nRF.
No. That would be like trying to connect your TV to your microwave. Both RF devices, but both work different ways and do different things.
Just because they are both rectangular boxes with a window in the front doesn't mean they are the same.
No, that is not possible: the ESP8266 is a WiFi SoC, and the nRF24L01 uses a proprietary protocol.
The fact that they both operate in the same frequency range doesn't matter if the protocols are different.
