Canonical has ultimately decided to drop support for the 32-bit live ISO release of Ubuntu distribution. With most of the architecture today being 64-bit, it was only a matter of time that Linux distros stop releasing 32-bit ISOs.
Confirming the development, Canonical engineer Dimitri John Ledkov writes, “…remove Ubuntu desktop i386 daily-live images from the release manifest for beta and final milestones of 17.10 and therefore, do not ship ubuntu-desktop-i386.iso artifact for 17.10.”
It is worth noting that Canonical is only ceasing the building of 32-bit Ubuntu Desktop Live ISO. The company will continue to focus on i386, which is becoming more of a purpose-built architecture for embedded devices.
Canonical mainly wants to focus its efforts on the Internet of Things (IoT) project, where x86-32-bit is still very common.
Installation possible on 32-bit machines
You can continue to install Ubuntu on your 32-bit machines. However, Canonical will no longer release any new live ISO for 32-bit machines.
Furthermore, Canonical will continue to release minimal and network installation ISOs for a 32-bit hardware. These images will receive updates and security patches until the next announcement.
Rise of 64-bit hardware
Alongside Canonical, open source distributions such as Arch Linux have also lately phased out 32-bit support to encourage users to switch to newer hardware.
The 64-bit processors started becoming common since the launch of AMD Opteron and Athlon 64 in 2003. Today, every single mainstream processor available in the market is based on either AMD64 or Intel 64 architecture.