I recently pulled a Linksys EA4500 out of storage for evaluation. The first thing I wanted to do was to update the firmware for the device.
https://www.linksys.com/us/support-article?articleNum=148385 offers the latest version of the firmware, which is 3.1.7
as of this writing.
However, we can see with the filename that its probably encrypted: FW_EA4500V3_3.1.7.181919_prod.gpg.img
When I run binwalk I don't get any meaningful results, confirming my suspcicions: