Remember the standard advice for all things running: we are an experiment of one and you need to find what works best for you.
You haven't said what distance you're warming up for or if you're talking about racing or merely training.
Yes, the research on this is discouraging or, at best, mixed. However, a great many health professionals will advocate for it - based on experience. Personally, I know my body and I know that if I do a certain stretch before I run then I don't get calf tightness. I ignore most other stretching directly before or after running. I do, however, stretch most mornings to keep my back loose.
If you are preparing to race then the length of your warmup is inversely proportional to the length of the race. So, if you're about to race 5km you might do a 1-2km light run as a warmup. This is so your muscles are in operating condition right at the start and you don't have to wait a minute or two before they're at full speed. However, on an ultra you've got plenty of time for things to get going so nobody bothers.
If you are out to do a speed training session then generally you would want a few kms of a light run first so that your legs are operating at peak. You're speed training to run fast when your legs are in that state so you need to get into that state first.