pfSense

1. Install 2.2.6 (I used an APU.2C2)
2. Install haproxy
3. Upgrade to 2.3.5

Configuring firewall......done.
Generating RRD graphs...done.
Waiting for Internet connection to update pkg metadata and finish package reinstallationUpdating pfSense-core repository catalogue...
Fetching meta.txz: . done
Fetching packagesite.txz: . done
Processing entries: . done
pfSense-core repository update completed. 7 packages processed.
Updating pfSense repository catalogue...
Fetching meta.txz: . done
Fetching packagesite.txz: .......... done
Processing entries: .......... done
pfSense repository update completed. 488 packages processed.
All repositories are up to date.

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.
Updating database digests format: .... done
The following 23 package(s) will be affected (of 0 checked):

Installed packages to be REMOVED:
        unbound-1.6.6
        pfSense-2.3.5
        rrdtool-1.7.0_1
        glib-2.50.2_6,1
        python27-2.7.14
        wol-0.7.1_3
        dnsmasq-2.78,1
        php56-gettext-5.6.31
        python2-2_3
        pecl-rrd1-1.1.3
        pfSense-Status_Monitoring-1.6.2
        bind-tools-9.11.2
        strongswan-5.6.0
        php56-pfSense-module-0.13_1

New packages to be INSTALLED:
        pfSense-pkg-haproxy: 0.54 [pfSense]
        haproxy: 1.7.9 [pfSense]
        lua53: 5.3.4 [pfSense]

Installed packages to be UPGRADED:
        check_reload_status: 0.0.7 -> 0.0.8 [pfSense]

Installed packages to be REINSTALLED:
        pkg-1.10.1_1 [pfSense] (ABI changed: 'freebsd:10:x86:64' -> 'freebsd:11:x86:64')
        libedit-3.1.20170329_2,1 [pfSense]
        ntp-4.2.8p10_2 [pfSense] (ABI changed: 'freebsd:10:x86:64' -> 'freebsd:11:x86:64')
        libevent-2.1.8 [pfSense]
        gettext-runtime-0.19.8.1_1 [pfSense]

Number of packages to be removed: 14
Number of packages to be installed: 3
Number of packages to be upgraded: 1
Number of packages to be reinstalled: 5

The operation will free 130 MiB.
5 MiB to be downloaded.
[1/23] Fetching pkg-1.10.1_1.txz: .......... done
[2/23] Fetching pfSense-pkg-haproxy-0.54.txz: ......... done

[...]

Checking integrity... done (0 conflicting)
[1/23] Deinstalling pfSense-2.3.5...
[1/23] Deleting files for pfSense-2.3.5: .... done
[2/23] Deinstalling pfSense-Status_Monitoring-1.6.2...
[2/23] Deleting files for pfSense-Status_Monitoring-1.6.2: ....... done
[3/23] Deinstalling php56-pfSense-module-0.13_1...
[3/23] Deleting files for php56-pfSense-module-0.13_1: ...... done

[...]

Loading package configuration... done.
Configuring package components...
Loading package instructions...
Shared object "libssl.so.8" not found, required by "haproxy" 
Shared object "libssl.so.8" not found, required by "haproxy" 
Shared object "libssl.so.8" not found, required by "haproxy" 
Shared object "libssl.so.8" not found, required by "haproxy" 
Custom commands...
Executing custom_php_install_command()...Shared object "libssl.so.8" not found, required by "haproxy" 
done.
Menu items... done.
Services... done.
Writing configuration... done.
Starting syslog...done.
Starting syslog...done.
Starting CRON... done.
 Starting package haproxy...done.
pfSense (pfSense) 2.3.5-RELEASE amd64 Mon Oct 30 11:08:06 CDT 2017
Bootup complete

FreeBSD/amd64 (pfSense.localdomain) (ttyu0)

Fatal error: Call to undefined function pfSense_fsync() in /etc/inc/config.lib.inc on line 204

Call Stack:
    0.0035     214144   1. {main}() /etc/rc.banner:0
    0.0070     214960   2. require_once('/etc/inc/config.inc') /etc/rc.banner:56
    0.4121     276944   3. parse_config() /etc/inc/config.inc:219
    0.4732     369128   4. generate_config_cache() /etc/inc/config.lib.inc:175

PHP ERROR: Type: 1, File: /etc/inc/config.lib.inc, Line: 204, Message: Call to undefined function pfSense_fsync()
 0) Logout (SSH only)                  9) pfTop
 1) Assign Interfaces                 10) Filter Logs
 2) Set interface(s) IP address       11) Restart webConfigurator
 3) Reset webConfigurator password    12) PHP shell + pfSense tools
 4) Reset to factory defaults         13) Update from console
 5) Reboot system                     14) Enable Secure Shell (sshd)
 6) Halt system                       15) Restore recent configuration
 7) Ping host                         16) Restart PHP-FPM
 8) Shell

Now, the system is dead.