I would say GPU/carte graphique dédié(e)1 or GPU/carte graphique indépendant(e).
The OQLF translates 'discrete component' (i.e. sth like a resistor, a capacitor, or a transistor compared to integrated circuits) to composant distinct and lists composant discret as an alternative from France Terme. I'm not convinced that distinct is a great choice here, nor that carte graphique distincte would be either.
Note that discret is in its mainstream acceptation a false friend. It then corresponds to the English 'discreet'.
A noisy discrete GPU is not discreet ;-)
We wouldn't use GPU discret in French because that would risk to be understood as discreet GPU.
The Latin discretus (separated) evolved through Medieval Latin to mean 'discreet, prudent' and gave the main meaning of the French
discret while the original meaning ('discrete') was only used by scholars and is now still restricted to scientific contexts.
1 Dédié started as an anglicism from 'dedicated'
Dédié, en informatique (OQLF)
Dans le domaine de l’informatique, champ reconnu pour son recours aux emprunts, dédié, comme synonyme de spécialisé, se dit de ce qui est conçu pour un usage spécifique; ce sens est aujourd’hui enregistré dans les dictionnaires et il semble qu’il soit maintenant trop tard pour éviter l’emprunt dans ce domaine.