This site is designed to find the set of bikes that match the specifications you want in a frame. The focus is frame geometry, but there are also filters for material, suspension correction, UDH compatibility, sliding dropout, handlebar (flat or drop), axle spacing, maximum tire width, cost, and more.
This site classifies gravel bikes into Racy, Relaxed, and Rowdy styles based on their frame geometry. This is somewhat unique – most websites or podcasts that I know of categorize gravel bikes as “more racy” or “more mountain bikey”
Also…some hardtail mountain bikes are included because some hardtails make really good gravel bikes.