pfSense

You need to select the Security/Errata only branch in update settings.

Security/Errata is not a choice there. I have Stable, Development or Next Major Version.

Next major version obviously fails as there's no Nano in 2.4 but Dev shows the expected 2.3.5 snapshot.

[2.3.4-RELEASE][admin@xtm8.stevew.lan]/root: cat /usr/local/share/pfSense/pkg/repos/pfSense-repo-devel.conf
FreeBSD: { enabled: no }

pfSense-core: {
  url: "pkg+https://beta.pfsense.org/packages/pfSense_v2_3_amd64-core",
  mirror_type: "srv",
  signature_type: "fingerprints",
  fingerprints: "/usr/local/share/pfSense/keys/pkg",
  enabled: yes
}

pfSense: {
  url: "pkg+https://beta.pfsense.org/packages/pfSense_v2_3_amd64-pfSense_v2_3",
  mirror_type: "srv",
  signature_type: "fingerprints",
  fingerprints: "/usr/local/share/pfSense/keys/pkg",
  enabled: yes
}

>>> Updating repositories metadata... done.
2.3.5.a.20171022.0705 version of pfSense is available

[2.3.4-RELEASE][admin@xtm8.stevew.lan]/root: pfSense-upgrade
>>> Updating repositories metadata... 
Updating pfSense-core repository catalogue...
pfSense-core repository is up to date.
Updating pfSense repository catalogue...
pfSense repository is up to date.
All repositories are up to date.
**** WARNING ****

NanoBSD platform is no longer supported.

You can find instructions on how to convert it
/usr/local/libexec/pfSense-upgrade: to Full Installation at http://bit.ly/2wDinm8: not found

You have some weird system. It definitely is a choice here, and for others.

https://forum.pfsense.org/index.php?topic=138285.msg756148#msg756148