ZeroTier as a ReadyCloud replacement.

Following suggestions in the post...

root@mynas:/home/admin# apt-get install ./libstdc++-arm-none-eabi-newlib_4.9.2-10+7~bpo8+1_all.deb
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'libstdc++-arm-none-eabi-newlib' instead of './libstdc++-arm-none-eabi-newlib_4.9.2-10+7~bpo8+1_all.deb'
The following additional packages will be installed:
libnewlib-arm-none-eabi libnewlib-dev
Suggested packages:
libnewlib-doc gcc-arm-none-eabi
Recommended packages:
gcc-arm-none-eabi binutils-arm-none-eabi
The following NEW packages will be installed:
libnewlib-arm-none-eabi libnewlib-dev libstdc++-arm-none-eabi-newlib
0 upgraded, 3 newly installed, 0 to remove and 19 not upgraded.
Need to get 47.3 MB of archives.
After this operation, 351 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://archive.kernel.org/debian-archive/debian jessie/main armel libnewlib-dev all 2.1.0+git20140818.1a8323b-2 [224 kB]
Get:2 http://archive.kernel.org/debian-archive/debian jessie/main armel libnewlib-arm-none-eabi all 2.1.0+git20140818.1a8323b-2 [13.3 MB]
Get:3 http://archive.kernel.org/debian-archive/debian jessie-backports/main armel libstdc++-arm-none-eabi-newlib all 4.9.2-10+7~bpo8+1 [33.8 MB]
Fetched 47.3 MB in 7s (6,332 kB/s)
debconf: delaying package configuration, since apt-utils is not installed
Selecting previously unselected package libnewlib-dev.
dpkg: warning: files list file for package 'libclamav9:armel' missing; assuming package has no files currently installed
(Reading database ... 20962 files and directories currently installed.)
Preparing to unpack .../libnewlib-dev_2.1.0+git20140818.1a8323b-2_all.deb ...
Unpacking libnewlib-dev (2.1.0+git20140818.1a8323b-2) ...
Selecting previously unselected package libnewlib-arm-none-eabi.
Preparing to unpack .../libnewlib-arm-none-eabi_2.1.0+git20140818.1a8323b-2_all.deb ...
Unpacking libnewlib-arm-none-eabi (2.1.0+git20140818.1a8323b-2) ...
Selecting previously unselected package libstdc++-arm-none-eabi-newlib.
Preparing to unpack .../libstdc++-arm-none-eabi-newlib_4.9.2-10+7~bpo8+1_all.deb ...
Unpacking libstdc++-arm-none-eabi-newlib (4.9.2-10+7~bpo8+1) ...
Setting up libnewlib-dev (2.1.0+git20140818.1a8323b-2) ...
Setting up libnewlib-arm-none-eabi (2.1.0+git20140818.1a8323b-2) ...
Setting up libstdc++-arm-none-eabi-newlib (4.9.2-10+7~bpo8+1) ...

Then performed apt-get update...

Then tried 1.8.4 again...

root@mynas:/home/admin# apt-get install ./zerotier-one_1.8.4_armhf.deb
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'zerotier-one:armhf' instead of './zerotier-one_1.8.4_armhf.deb'
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
zerotier-one:armhf : Depends: libstdc++6:armhf but it is not going to be installed
E: Unable to correct problems, you have held broken packages.