I don’t. Proper bracing and doing warmup sets of whatever exercise I’m planning on doing has always been enough, although I usually don’t lift very heavy. Minimum of 8 reps on squats for example.

If I were to have lower back problems I would simply look at different exercise examples on youtube and try them out. Different exercises will work for different folk, there is no best exercise for waming up the lower back. I would also try lifting even lighter.

I wiggle my hips a bit, bend over 2-3 times and try(!) to touch my toes with stretched legs. Do 5 body weight squats and then I just get into it. Warming up is overrated. Just get your blood flowing with some basic simple stuff and start working. Don’t spend more than 2-3m on your warmup.

I do a quick set of rdl and then back squat with just the barbell to get myself into a good state of mobility

I used to do stretches between sets of back squat but I cut that out as well l. This likely did me more harm then good. As others have stated, proper bracing / engagement of your core will see you through.

I still pre exhaust on leg extension before back squat but other than that, I feel prepared getting into a good 5*5.