Wait I had an amazing idea: Dcxdp but instead of Danny ending up in the batfam Danny is in metropolis
What if Clark is absolutely sure Danny was a kryptonian with a health condition? So I like the idea of Danny occasionally having to make sure his heart is still beating while in human form and the little stutters sound like a small heart condition to Clark, now this would normally not be a problem as Clark would just keep an eye on Danny but Danny sometimes gets too focused on something and forgets to check his heartbeat and it stops and when he realizes he taps his chest to “get it going again”. Also Clark always just happens to be around when a ghost shows up (yes they followed Danny, they need their enrichment) so he sees and feels the subfreezing mist that comes from Danny’s mouth and sometimes see’s Danny’s eyes glow green accidentally and knows that despite Danny’s “condition” Danny is much stronger than a human should be because of an accident that happened that ended up with Danny lifting he shouldn’t be capable of.
The thing is every time Clark tries to talk to Danny to see if “Danny knows what he is” Danny seems to disappear and somehow Clark can’t follow (hard to track a ghost lol). This culminates in Clark taking the nuclear option: Clark breaking into batman’s cave to use his computer to find out anything he can on Danny. This then leads to Batman coming down to suit up for the first time after a full week of having to show up as Bruce to galas to see a sleep deprived and obviously heavily caffeinated Clark with a bulletin board that looks oddly like a mess of conspiracy theories about Danny in front of the bat computer.