no ground bar in electrical subpanel
There is a ground after all

The ground bars on most loadcenters, when fitted, are located on the far left and right sides of the enclosure, so they often get buried behind wiring in the gutter spaces, and this appears to be the case in your installation.  (In your third photo, you can just see one peeking out from behind the wiring in the bottom right-hand corner of the picture.)

Your fourth photo also shows the bare fat wire that is the ground in the feeder cable (what appears to be a type SE-R cable), running off what I presume is a lug on the left-hand ground bar, and the empty hole on the left-hand side of the neutral jumper bar, next to the red wire, is correct for a subpanel (it is where the bonding screw goes when this panel is used as a main).