hahahahaha WELL this doesn't bode well for me as someone who's written several koobi fics, which you've probably not enjoyed or been interested in lol 😬 for me it's about canon tbh! the energy of their relationship irl is really up my alley and i'm very into both of them as people, so i enjoy reading and writing fics that feature them heavily as characters. i have a bunch of fic recs for them here, but it's a LOT to go through, so a few good ones that come to mind across a few different genres are:

common love was never for us by DaydreamNoona, a fantasy/detective/reincarnation AU with some really incredible mythology and foreshadowing
current by contra_band, a short post-disbandment AU that is so beautiful and measured and feels like the flowering of something entirely new
Three's A Crowd by onlyhuman, a canon compliant filthy threesome with an OFC
Just Add Water! by hardweeping, a ridiculous and funny and somehow still very hot AU where hobi literally grows jk his dream boyfriend from a toy sponge
love me like a summer fling by thistidalwave, a fun summer beach friends with benefits AU with lifeguard hobi
and i do enjoy my own fics too if you ever wanted to give that a shot~

honestly i just like them and i like to read fic about them!