On Canadair RJs you can manually arm or disarm the GLD function if the automatic arming function isn't working, but you can't force a manual deployment of the GS themselves. (arming is a prerequisite for deployment, but arming alone wont force deployment)
You do, I believe, still have direct control of the flight spoilers on-ground if the GLD function doesn't work, but the GS themselves won't deploy. So you'll effectively get partial GLD in that case.