Here is a great beginner exercise for improving your gluteus maximus, which is a very important muscle to support your low back.
As a Personal Trainer one of the first exercises I do with many of my clients is the glute bridge. This is a way for me to make sure the glute muscles are firing. If the glutes aren’t firing, then you may experience low back discomfort when doing this exercise. Also there may be a muscle imbalance in the hips, that should be addressed, this is information I need to design an exercise program.
The bridge is also a great way to stretch the hip flexors, which may get tight when sitting too much. It’s also a great exercise to recruit the gluteal muscles with minimizing the TFL. Check out this article form Pub Med explaining.