Some of the services have moved, with more to follow, from First to Northern(Arrriva).
Their new rolling stock for this area hasn't been fitted out for carrying bikes, so far. .
I've signed it, although last time I traveled on TPT with my bike & no reservation, the guard said I was fine, as most of the guards didn't agree with the new policy anyway
Some of Northern's current stock doesn't have any bike spaces. A few years ago I was traveling from Leeds to Doncaster on a refurbished class 321 train & after walking the full length of the train, I found there was no bike space
You just have to leave it in a doorway