yaoi where the mc actually gets with the nice, childhood friend-esque 2nd lead instead of the bastard 1st one
https://www.mangago.me/read-manga/the_god_of_pain_s_groom/
not child hood friend but the mc chooses the objectively better 2nd lead
there was this one omegaverse where the alpha literally smelled him through the vents when he was trying to escape
edit: more details was that it happened in the beginning chapters, and the alpha was very corporate? some kinda CEO I think. he was very determined to find his ass. also I think there were some researchers in it or something
This?
https://www.mangago.me/read-manga/the_promise/
There's a scene where the MC tried to escape thru the vents. This is not an omegaverse though.
there was a yaoi about an actual old man who was kinda balding who was a researcher or something?? and then made a guy into a zombie and fell I love and the ending was sad
He wasn't that old he was just a bit unfortunate looking
And yes it's Sleeping Dead by Asada Nemui
https://www.mangago.me/read-manga/sleeping_dead/

the girl was like a gang leader(?) and the guy was an aspiring idol. she offers him a contract to get married together but obviously hes resistant and he also had some kind of family drama