/usr/share/epiphany-browser/branding.conf is in epiphany-browser-data 3.14.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | [User Agent]
Vendor=Debian
VendorSub=unstable
VendorComment=3.14.1-1
|