Is it possible to connect L298N motor controller to Navio2?
There is no ready solution for such kind of application, but if you are experienced in programming and electronics it should be possible to make it work.
As far as I know, the L298N motor driver requires PWM for speed control and digital input (logical 0 or logical 1) to operate motor spinning direction. If I recall right, it should be controlled with a 5V signal.
Navio2 allows both PWM and GPIO control, but its PWM voltage level is 3.3V which means you can hardly integrate them directly.
So it looks like that the task becomes more complicated since you need to shift the 3.3V PWM to 5V PWM using a transistor or something like that.
The L298N needs two on/off inputs per motor channel to control forward/reverse/braking/free wheeling. I guess the easiest way to use the L298N with ardurover/Navio2 is to put an arduino in between. The arduino reads the two PWM outputs (or mavlink or sbus) coming from the autopilot and translates it to two PWMs + 4on/offs for the two motor channels. I did it this way some years ago and it worked well.