I have found the solution and I'm going to share it in here so anyone with that problem can fix it or the developers can see a way to fix it.
Basically I had Steam installed through Flatpak, and somehow that broke Terraria. When i reinstalled Steam through a .deb file, Terraria was ok again.
i just installed terraria in my Ubuntu 18.04 machine and everytime i open the game, the main menu is missing, but i know it is there because i can click in the menus, i think the font is missing! how do i fix this?