Hi @krys,
Welcome to the forum!
We haven’t tested Navio2 with any specific flow sensors, so I can’t comment on it. But maybe Marc can share his experience. I’ve found mention of the Matek 3901 LOX sensor testing on the UART port in this thread.
I can confirm that there’s no CAN port and there’s an I2C port on Navio2.
We haven’t tested the Hex Hereflow sensor, so I can’t specify if this sensor supports the I2C connection. There’s only mention of a CAN port on the website Marc provided tho.