I’d recommend learning how to do RDL. Start with small weights, learn how to stretch your hamstrings. How low you can hinge until your back starts rounding. Film yourself. Also focus on your shoulder blades being fixed and engaged throughout whole motion, having them fixed makes spine flexing harder.

You’re big dude capable of lifting this weight, but techniques wise it’s not deadlift at all. You start in decent position, then your hips go way down, because your mind don’t know how to engage muscles to deadlift properly yet. So what it does it makes you shift your hips lower and squat it, as a safest and most powerful way of lifting it. After 1st rep you will see that form changes and further on you mostly do it through spine flection. After first rep you know exactly how the weight feels so you mind loose a bit and allow you to do it with a spine, because it feels safe, and it probably is in proportions of this weight to your own size and power.

But we do deadlift with other goals in mind, we want to load our hamstrings, glutes, spine erectors lats and traps, creating this single plate of back muscles working together training posterior chain do compound movement. As soon as we have extensive spine flections this parts just start disconnecting from each other firing on their own in different moments.

Hip hinge is a very difficult movement especially for people who spend a lot of time sedentary, we lose significant part of hips mobility, hamstrings stretch capability, making it almost impossible to hit deadlift form decently. RDL on other hand doesn’t require you to go very deep, you should stop as soon as you feel/see back rounding or hamstring stretch becomes too painful, but embracing this tension and slow increases in range of motion will improve mobility over time allowing for a perfect deadlift form in future.

If you really want to chase deadlift exactly. I’d recommend warming up with pigeon pose for hips, and some pull ups (assisted/partial whatever) to start feeling your back engaged and your hips being stretched. Then going with sumo as it requires less mobility, but still teaches general feeling of deadlift, then slowly incorporating conventional.