You should search the Trisquel forums for "GA-G41M-ES2L", as there are
several other discussions of the same topic - which video card to use with
this board.
Some of the best information comes from member vita_cell, who has experience
with different libreboot and coreboot setups with different graphics cards
with this motherboard:
https://trisquel.info/en/forum/graphic-card-recomendation-libreboot-ga-g41m-es2l
Also some other discussions:
2016 -- https://trisquel.info/en/forum/which-video-card-best-choice-today
2018 --
https://trisquel.info/en/forum/help-graphics-card-selection-desktop-build
