Ok I think I got it - I am on Debian 8 aka this “Jessie” I hear so much about, and I need to update to Debian 9 “Stretch” - trying to do this now.
Here’s an article I found for others who might be in this conundrum: https://linuxconfig.org/how-to-upgrade-debian-8-jessie-to-debian-9-stretch
abcd567, many thanks for the reply. I wanted to may gain changes to the programs.
Download .deb packages matching your Architecture, then install by:
sudo dpkg -i [downloaded package name]
Download pages (scroll down to bottom of page for download links)
NOTE:
These are sid, i.e. unstable packages.
Your OS is Debian, which means you are NOT using Raspberry Pi.
The dump1090-fa package installed by sudo apt-get install dump1090-fa gets .deb package from flightaware repository. This package is custom made for Raspbian OS and architecture armv6/7. It will not install on Debian running on x86 amd64 i386 architecture.
Try to built it from source code. Use Joe Prochazka’s automated install
sudo apt-get install git
git clone https://github.com/jprochazka/adsb-receiver.git
cd adsb-receiver
./install.sh
Select dump1090-fa, and say NO to everything else.
OK, so if others have been running their feeder for a while and are on the Debian 8 “Jessie” like me - I survived my first major Linux OS upgrade, all over ssh! 
That article I linked above (and some of the comments) got me through it by following it to the T. It took a considerable amount of time (over an hour, and googling some of the error/warning messages during the upgrade) Make sure you queue up some good TV shows, Youtube videos, go walk the dog, etc - once you say “apt-get dist-upgrade” and accept the changelog. (hit “q” for the uninitiated, like me. Also, let the OS restart services as it upgrades them, as we aren’t mission-critical as much as we may love this hobby 
) Once upgraded, I was still unable to install dump1090-fa successfully. I then ran apt-get --fix-broken-install and rebooted the RPi.
Finally, running the install again, I was able to get it running. I rebooted everything one more time and seem to have some good stuff @ IP:8080 - which is different than my old setup. I’ll make sure over the next day that FR24 etc all work with this dump.
All in all, I would not recommend this upgrade, and caution that you will dive deep into Linux if you do this, if like me you were just wanting the 3D view. Likely, it’s probably best to do the upgrade, but you need to be ready.
Feeders such as Piaware, FR24, Planefinder, Adsbexchange, Radarbox24, Opensky-network, etc will NOT be affected.
With extreme respect to @abcd567 This is somewhat false. My FR24 feeder died as soon as I removed dump1090-mutability. I also lost all the customizations I did to that page (expected). The good news is that once you install and get dump1090-fa working, it’s a ‘drop-in’ replacement and FR24 starts working again, even with the different lighthttpd ports, etc.
It is still not clear to me. You say “rebooted RPi”, then say “Debian Jessie”. This is confusing as normally RPi users used "Raspbian Jessie"and not “Debian Jessie”.
Just out of curiocity, can you post output of following two commands?
cat /etc/os-release
uname -a
pi@ryanspi:~ $ cat /etc/os-release
PRETTY_NAME="Raspbian GNU/Linux 9 (stretch)"
NAME="Raspbian GNU/Linux"
VERSION_ID="9"
VERSION="9 (stretch)"
ID=raspbian
ID_LIKE=debian
HOME_URL="http://www.raspbian.org/"
SUPPORT_URL="http://www.raspbian.org/RaspbianForums"
BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"
pi@ryanspi:~ $
And
pi@ryanspi:~ $ uname -a
Linux ryanspi 4.9.35-v7+ #1014 SMP Fri Jun 30 14:47:43 BST 2017 armv7l GNU/Linux
It’s entirely possible (and likely) I’m not using the right terminology. I’m not that familiar with Linux, and just went through a whole OS upgrade in order to get two new packages.
My statement that feeders will not be affected was for the final situation, i.e. after completion of replacement of mutability by fa.
What you described is the transition stage: mutability is removed but fa not installed. Defenitely during the transition period there is no dump1090 available, and all feeders will fail.
Totally agreed - I just wanted to be clear to noobs like me - if you remove your existing dump1090, of course everything that depends on it will fail until you fix it. And the fix might be an hour+ long OS upgrade to Linux for which, you’re not prepared.
Almost all of us have passed through similar unexpected and frustrating experience. This is part of learning Linux.
Glad that finally you succeeded in upgrading your OS, and could finally install dump1090-fa 
Thank YOU for all your input and super-fast replies. You certainly live up to your avatar, and I feel as though I am but a padawan to the ADS-B Zeus, learning from the master.
Surely though, others have an easier method to upgrade their Raspberry Pi’s? I can’t imagine everyone with an RPi has to go through what I did to do the Stretch upgrade.
I dont know about others, but for a major upgrade like this one, I formatted microSD card of Jessie, downloaded Stretch image, and wrote it to microSD card.
(1) Downloaded Raspbian Stretch Lite image
Raspberry Pi OS – Raspberry Pi
(2) Shutdown Pi, slipped out microSD card, slipped it into card reader of Desktop, wrote Stretch image to microSD card.
(3) While card still in card reader, clicked it open and created file ssh.
(4) Ejected microSD card from Desktop, slipped it into Pi, and powered up. Run sudo raspi-config, set locale and time zone, and expanded file system, rebooted Pi.
(5) Installed Piaware data feeder and dump1090-fa by following commands
wget http://flightaware.com/adsb/piaware/files/packages/pool/piaware/p/piaware-support/piaware-repository_3.6.2_all.deb
sudo dpkg -i piaware-repository_3.6.2_all.deb
sudo apt-get update
sudo apt-get install piaware
sudo apt-get install dump1090-fa
sudo piaware-config feeder-id xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
sudo piaware-config allow-auto-updates yes
sudo piaware-config allow-manual-updates yes
sudo reboot
(6) Installed Flightradar24 feeder by following command
sudo bash -c "$(wget -O - https://repo-feed.flightradar24.com/install_fr24_rpi.sh)"
The above command installed fr24feed and automatically started signup/configure process. At very first step of signup i.e. when it asked email address, pressed Ctrl+c to break the process and got command prompt. Then configured by following method
sudo nano /etc/fr24feed.ini
This file at this stage has only 3 lines. Added following lines
receiver="beast-tcp"
host="127.0.0.1:30005"
fr24key="xxxxxxxxxxxxxx"
Replaced xxxxxxxxxxxxxxx by actual fr24key
Restarted fr24feed by following command
sudo systemctl restart fr24feed
After 5 minutes, checked status
fr24feed-status
There is a problem connecting to FR24 server due to its incompatibility with IPv6. Did following workaround:
sudo nano /etc/gai.conf
In this file found the following line:
#precedence ::ffff:0:0/96 100
Uncommented this line so it looks like:
precedence ::ffff:0:0/96 100
Now Pi will prefer IPv4
Restarted fr24feed
sudo systemctl restart fr24feed
(7) Installed Planefinder data feeder by following commands
wget http://client.planefinder.net/pfclient_4.1.1_armhf.deb
sudo dpkg -i pfclient_4.1.1_armhf.deb
Afrer installation is completed, configured pfclient by going to following page
IP-OF-PI:30053
Entered sharing code, latitude, longitude, host 127.0.0.1 port 30005
Assume then adding ADSBexchange is just a case of running their script from the web page?
Geffers
Yes. You can add any other feeder by using their scripts.
.
.
Absolutely correct.
For quick reference, here is how to run their script
sudo apt-get install git
git clone https://github.com/adsbxchange/adsb-exchange.git
cd adsb-exchange
chmod +x setup.sh
sudo ./setup.sh