Strange, mine shows up the exact same way. Does Reicast say “Using PS3 map” during startup? (If you launch it from command line and then exit right away, you’ll still have the launch log on screen and should see that. SHIFT+PGUP will scroll back up through your terminal buffer a short way too!)
I will have some time to tinker more with it this weekend and will see what I can figure out.
Are your 4 main Dreamcast buttons the START, SELECT, L3 and R3 buttons? If so, it’s using the default map and not detecting your controller for some reason.