Any of the sca approved drip brewers are perfect for this, but most of them arent exactly cheap. I use a technivorm moccamaster for groups or anytime I’m feeling lazy.

Cheapest I’ve found in the us is the Dunkin medium roast, but as others have said grinding it with a burr grinder (not a blade grinder) is a huge difference. You can buy a bag of beans and have them ground at some supermarkets though. True bulk for a community break room is gonna be hard. Best of luck.