Installing Windows 2019 iso should fit on a single DVD.
I recently downloaded a 2019 Server ISO file and discovered it is too big to write to a DVD. But Windows Server 2019 also requires a GPT partitioned bootable drive. The only thumb drives I had available were too small, or were initialized as MBR. And then I discovered that a lot of thumb drives can't be initialized as GPT drives. What with that, and the previous time spent tracking down potential problems, I have now been working on updating a server to 2019 for a month, and still have not even started the actual update.