Band around the ankles, kick one leg straight back.
Keep your torso upright and lift from the glute, don't lean forward to swing the leg.
Kicking one leg straight back against an ankle band is hip extension distilled, the glute max drives the leg behind you with the hamstrings assisting, and the band's tension peaks exactly at the squeeze. The standing side is training too, holding your pelvis level while the other leg works. The honest range is short, which is precisely what keeps the work in the glute instead of the lower back.
Not far, genuine hip extension runs out after a modest arc. Anything past that comes from arching your lower back, which is exactly what you are trying not to train.
Same movement pattern, different resistance. The cable stack loads the whole arc more evenly and heavier, the band peaks at the squeeze and goes anywhere, both are valid tools for the same glute.
You are leaning forward and swinging the leg rather than extending from the hip. Stand tall, brace, shrink the range, and squeeze the glute deliberately at the end of each rep.
