Deadlifts work the back a ton, snatches work the back in the first half of the movement. You're good. Being sore is good

This. I did a walk in to a box in Kitty Hawk NC when I was on vacation. Snatch balances and then 50 hang squat snatches for time. The lower back was mildly sore the next day and fine after that.

Deadlifts are all legs. If you are feeling your lower back, that means you were not using your legs enough in the lift. In the set up, make sure to get your butt down, keep a neutral spine, and fix your eyes about 4 feet in front of you so that your neck and back are one straight line. Give the bar some tension before picking it up. When you lift the bar, your upper body should rise up before your butt. If your butt is rising first, you are using too much of your back and/or the bar could be too heavy.

Deadlifts are all legs. If you are feeling your lower back, that means you were not using your legs enough in the lift. In the set up, make sure to get your butt down, keep a neutral spine, and fix your eyes about 4 feet in front of you so that your neck and back are one straight line. Give the bar some tension before picking it up. When you lift the bar, your upper body should rise up before your butt. If your butt is rising first, you are using too much of your back and/or the bar could be too heavy.

You have to use your lower back to straighten up at the top. I had/have a SUPER weak lower back (used to throw it out all the time), but very strong legs, so I always feel it more in my lower back when I'm doing heavy weights (squat, deadlifts, kbs, etc).

Deadlifts are definitely not "all legs". Your spinal erectors and low back do a lot of work to transfer the force through your torso to allow you to hang onto the bar with your arms but use your legs and glutes to do most of the work. That being said, if you don't keep everything tight in your back, you could end up with "bad" low back pain. I still have a grumpy low back from doing heavy deadlifts ~10 days ago with a rounded back. It started hurting WHILE I was doing my lifts which is definitely a bad sign. If it doesn't hurt until the next day, it is mostly likely just DOMS/muscle soreness which is fine and nothing to be concerned about. I know we are conditioned to worry about low back pain but your low back muscles can get sore from lifting just like your quads or triceps can.

Also just realized that OP did snatches as well as deadlifts--you could potentially not be bracing your abs enough at the top of the movement. I feel soreness from snatches more in my upper back/shoulders just because my body is still getting used to stabilizing the bar with such a wide grip.

So, you never experience lower back soreness after heavy deadlifts? She said she was experiencing it the next day, not during the workout. Just because you have done heavy DLs for multiple reps and not experienced soreness the next day, does not mean it's not possible for other people.

If I go super heavy on DLs or do a WOD with heavy KBS (24kg+), my lower back will be sore the next day a bit. I've talked to my coaches about it and it's more about the fact that my lower back was so weak (from terrible posture and being sedentary) than doing the movement wrong since they check my form.

Also let's clarify that there is a difference between lower back muscle soreness and lower back PAIN. We've all been doing this long enough that we know the difference, I think it's just getting confused in some of the exchanges.