I was able to solve this with many thanks to @user535733 -- much appreciation.
First, I created a live bootable USB. Please NOTE: if you want to be able to make changes to your Ubuntu environment you will need to make a persistent live usb.
-- to create a bootable live usb that will not remember configurations or changes once you reboot -- follow this guide:
https://ubuntu.com/tutorials/tutorial-create-a-usb-stick-on-macos#1-overview
-- to create a persistent usb that will remember SOME changes when you reboot (like network config, etc) follow any of these guides -- note if you use the last one you will either need to buy the tool or compile it -- I bought it for $4.99...
option 1 -- How do you create a live persistent Ubuntu USB on a Mac that will boot to a Mac or PC?
option 2 -- https://apple.stackexchange.com/questions/285722/persistent-ubuntu-boot-usb-macos-sierra
the source is here if you want to build it yourself:
https://github.com/SevenBits/Mac-Linux-USB-Loader/wiki/Using-Persistence-with-Mac-Linux-USB-Loader
2 -- with a live usb version, boot your mac using the instructions for either option above -- note if using persistent you need to follow the boot instructions to boot persistent
3 -- once your Ubuntu system is up, get networking going (wired ethernet is easiest)
Note -- you will see an Ubuntu installer on the desktop -- you will use this in a future step to install FULL 18.04 onto your new usb
4 -- insert a new USB into the system
5 -- open terminal and run df -h
Note which device is your new usb in my case it was /dev/ssb -- see comments from user535733 in the comments of this post for more helpful info
6 -- start the Ubuntu installer by double clicking on it -- if it asks to unmount partitions, let it
7 -- as the installer runs it will ask you to pick from a drop down which device you want the install to go to -- BE SURE you pick the new usb that you identified in step 5 above.
8 -- let the install go -- it will take a long time. I chose to install updates and complete drivers - pick what works for you.
Once complete power down your system, remove the original live USB (not the new one) and boot your mac by holding down the option key and pressing the power button. Once the boot loader comes up select the new full ubuntu USB to boot from -- it will take some time to come up -- be patient
9 -- post install note -- when I wanted to go back to my mac os the system kept loading a grub boot loader. I was able to get around this by resetting NVRAM (hold option+command+P+R keys and power up) see this Apple note: https://support.apple.com/en-us/HT204063
That's it -- I was able to create a FULL installed 18.04.4 LTS USB that will remember all the software I and and changes I made.
Again, many thanks to @user535733 for the help!
df -h
. That will tell you how each disk and partition is labelled (usually /dev/sda for each disk, /dev/sda1 for each partition). You can usually tell which is which by the sizes ("oh, there is my 64GB stick"). Write down exactly which label corresponds to the USB drive that you want to install Ubuntu upon. Close the terminal. Once you understand which disk label points to your second USB stick, then start the installer. When you see a prompt or a drop-down menu with disk labels on it, then make sure you select the correct disk label. – user535733 Feb 21 '20 at 22:09