trimming a 24" hollow core door?

It is possible but would be a PITA to do. You would only be able to trim the hinge side of the door since the other side is pre-bored for the door knob unless you buy a blank. Cut the 2" off the hinge side of the door. This should also remove all the wood frame on that side at the same time. Then you will have to remove the glued on door skin from the removed frame piece. Then you can put that piece back into the now narrowed door. You will need to glue and nail it in place again.

It would probably be a lot easier to buy a 1/10 - 6/8 (22" x 80") door than make it.

with the cheaply way those are made nowadays?

you can but there is only an inch of wood at each end, if you cut it that much you would need to add lumber to the edge you cut off then glue and clamp it tight for a while

you could do ..if a highly skilled carpenter ..but its not an easy task