Excerpts of announcement included below. For full announcement, see the debian-announce mailing list archives.
After 26 months of development the Debian project is proud to present its new stable version 9 (code name “Stretch”), which will be supported for the next 5 years thanks to the combined work of the Debian Security team and of the Debian Long Term Support team. Debian 9 is dedicated to the project’s founder Ian Murdock, who passed away on 28 December 2015.
The UEFI (“Unified Extensible Firmware Interface”) support first introduced in “Wheezy” continues to be greatly improved in “Stretch”, and also supports installing on 32-bit UEFI firmware with a 64-bit kernel. The Debian live images now include support for UEFI booting as a new feature, too.
A total of ten architectures are supported: 64-bit PC / Intel EM64T / x86-64 (amd64), 32-bit PC / Intel IA-32 (i386), 64-bit little-endian Motorola/IBM PowerPC (ppc64el), 64-bit IBM S/390 (s390x), for ARM, armel and armhf for older and more recent 32-bit hardware, plus arm64 for the 64-bit “AArch64” architecture, and for MIPS, in addition to the two 32-bit mips (big-endian) and mipsel (little-endian), there is a new mips64el architecture for 64-bit little-endian hardware. Support for 32- bit Motorola/IBM PowerPC (powerpc) has been removed in “Stretch”.
https://www.debian.org/News/2017/20170617
http://ftp.debian.org/debian/doc/dedication/dedication-9.0.txt
https://www.debian.org/releases/stretch/installmanual
https://www.debian.org/releases/stretch/releasenotes
Firmware Security 