without a barbell you can increase your pchain strength with leg curls ( this doesn't hit the glutes and lower back though, so you cannot just do this, you have to do another p-chain lift or you are going to be imbalanced ) and glute-ham-raises ( its better with a machine, but you can do natural ones).

I think you should do a whole plyos program instead of just starting with depth jumps, because they are pretty advanced. You can do bodyweight exericises to increase strength, and also do dumbell squats and lunges (to my knowledge, these do increase pchain strength as a secondary, but you will have to do more).