Danny, thanks for your excellent sleuthing on this.
One thing that does give me pause before I go ahead with this, and hopefully someone can confirm; Sony, of course, doesn't provide a MD5 for the file. Their website that you linked says,
Verify that the size of the "sony_atvotafull_2018_1604738100_naa_auth.zip" file is "1,350,895,941" bytes.
I show a decompressed size of
1.25 GB (1,350,895,695 bytes)
when I extracted into a folder.
So, fearing corruption, I redownloaded and extracted the file directly into the downloads directory. This shows the correct size,
1.25 GB (1,350,895,941 bytes)
These extractions are using winRAR on Win10.
Just wanted to point this out for other members looking to try this out.
Has anyone else bothered to check this or am I just being paranoid?