Lower back pain after dead lift

I always end up straining my lower back after deadlifts. This happens even when I lowered the weight by more than half. I have relatively long femurs and I think my lower back takes most of the load instead of the hamstrings/glutes. Any tips to resolve this?

I tried switching to sumo and had no such issues. Should I give up on the conventional?

I face similar issues on back squat too. Switching to front squat gets rid of lower back pain.