DF employs OpenGL for rendering, see file df_linux/g_src/renderer_opengl.hpp, so the GPU will be used if appropriate drivers are installed. "Text" tiles and graphics tiles are equally fast – they are always bitmaps under the hood, see df_linux/data/art/*.png.

There is also an ncurses renderer with plain Unicode text output for use in a terminal emulator which may be GPU accelerated, but most term software is not.