Hey there,
I’m getting the same issue. I have a super fast NVMe drive and 600 Mbps down internet. My unreal 4.27.2 is downloading at ~1MB/s. I have tried all of the presented fixes. I am located in Redmond, WA.
My download starts at 40 MB/s and gradually goes all the way down to 100 KB/s and even 0 KB/s and then stays at around 1 MB/s. It is going to take 5 hours to download.