For linux I think one of the most professional and affordable digital audio workstations is reaper. But it does not really matter what you use. My music production at the moment lives on my mac. I have too many paid plugins i like to use and i could not be bothered to get everything to run on my linux machine.

To learn I would say just try to immitate/copy the music that you love. Listen carefully and try to make something similar. If you want to make a good beat, listen to a good beat that you like and try yourself. And do not worry if it sounds shit at first. Everyones first beats sound shit haha. If you do not know where to start just search for tutorials on youtube. But try to also explore things on your own. There is no set way to do any of this. If you find something that sounds cool to you, use it.

Also join a forum like newgrounds for example to share your work and discuss music production with people.