All platforms using the 3.2 kernel are restricted to Jessie.

The ancient 3.2 ARM kernel for Helix4 has finally been replaced with 4.14.
The 3.2 kernel is too old to build under Stretch so any platforms still using it must be restricted to Jessie only.
Once these platforms are ported 4.14 the restriction can be removed.

packages/base/armel/kernels/kernel-3.2-lts-arm-iproc-all/PKG.yml

@@ -5,6 +5,7 @@ common:
   copyright: Copyright 2013, 2014, 2015 Big Switch Networks
   maintainer: support@bigswitch.com
   support: opennetworklinux@googlegroups.com
+  dists: jessie
 
 packages:
   - name: onl-kernel-3.2-lts-arm-iproc-all

packages/platforms/delta/armel/arm-delta-ag6248c/arm-delta-ag6248c-poe/platform-config/r0/PKG.yml

@@ -1 +1 @@
-!include $ONL_TEMPLATES/platform-config-platform.yml ARCH=armel VENDOR=delta BASENAME=arm-delta-ag6248c-poe REVISION=r0
+!include $ONL_TEMPLATES/platform-config-platform.yml ARCH=armel VENDOR=delta BASENAME=arm-delta-ag6248c-poe REVISION=r0 DISTS=jessie

packages/platforms/delta/armel/arm-delta-ag6248c/arm-delta-ag6248c/platform-config/r0/PKG.yml

@@ -1 +1 @@
-!include $ONL_TEMPLATES/platform-config-platform.yml ARCH=armel VENDOR=delta BASENAME=arm-delta-ag6248c REVISION=r0
+!include $ONL_TEMPLATES/platform-config-platform.yml ARCH=armel VENDOR=delta BASENAME=arm-delta-ag6248c REVISION=r0 DISTS=jessie

packages/platforms/qemu/arm/arm-qemu-armv7a/platform-config/r0/PKG.yml

@@ -1 +1 @@
-!include $ONL_TEMPLATES/platform-config-platform.yml ARCH=armel VENDOR=qemu BASENAME=arm-qemu-armv7a REVISION=r0
+!include $ONL_TEMPLATES/platform-config-platform.yml ARCH=armel VENDOR=qemu BASENAME=arm-qemu-armv7a REVISION=r0 DISTS=jessie