my friend, before anything else I warn you that I am new to all this, so I do not understand everything ... but I had exactly the same problem as you and I was able to solve it!
What I did was use Synaptic, and download the myspell-es package.
After that the myspell-es package appears as installed (in green) in Synaptic.
Then I right click on the package, and opened properties, there several tabs and I went to the tab "installed files", Here are the directories where the files were installed, for example: "/usr/share/hunspell/es_AR.dic" (Which was the one I used for texmaker and it worked!)
I hope to have been understandable, lucky!