I configured my Marantz SR7012 with my Triton ones for my front L-R, the Center XXL and Aon3 for my surround speakers (S L-R).
Configuration:
The Front L-R are connected with LFE wire with the Speaker set to Large and crossover to LFE at 80db
Surround speakers are set to Large as well.

The tone adjustments and speaker configuration on marantz was made correctly and tested.

The sound mode was set to Dolby surround.

Now when I looked at demo videos on YouTube for 5.1 Dolby, the sounds that are supposed to go to surround speakers end up going to Triton ones.
Anything that I am missing or misconfiguring?

Hi. Just so we understand, the surround channels are coming out of the fronts? What is coming out of the surrounds? All I can suggest is to double check that your speaker wires are connected to the correct terminals on the back of the marantz receiver and then run the test tones to confirm the correct speakers are playing. If you have already confirmed the test tones play to the correct speaker then it is most likely the source. Play a known source like a BluRay disc or a TV show (not a YouTube video with unknown origin as it could easily not have been audio encoded properly) to confirm.

Regarding setup, Front Tritons to LARGE, Subwoofer to YES, LFE to 120Hz, Aon 3 Surround to SMALL with 80 Hz Crossover.