Someone armed with an arduino a long-range controller for a boat, can it be possible to have the same features or qualities as the pixhawk?
No not really.
The arduino runs only one loop. The Ardupilot compatible boards can run several loops at different rates and are much more optimised for the job.
and taking out the pixhawk, which boards can be compatible, I thought that since I was armed at ease and being open source the arduino could run the mission planner, the pixhawk can hardly be bought here, there is a very large devaluation, that’s why we are looking for alternatives here
https://ardupilot.org/copter/docs/common-autopilots.html
You just have to work through the list and see what’s available in your area.
Maybe the navio board is something for you? I guess it’s a overkill for your purpose. But maybe you’ll find it useful.