Finally, success!
For anyone else who is having issues that may find this thread, I’ll type what worked. Be warned though that this is for OS ver2.0 specifically and I upgraded from v2.0.4 to v2.1.7 and I (clearly) don’t understand this stuff well enough to say what other hardware or firmware version combinations this works on. I’m also running this from Windows 10 which also differs from Linux, MAC and even other versions of Windows from what I’ve read.
For starters, you WILL need to install the drivers before plugging in the OS USB cable. Use the link two posts above and follow the instructions. Once that’s installed plug in the USB cable and open Device Manager to assure that your machine sees the OS as USBtiny (mine was under libusb-win32 devices) and then proceed with the code mentioned in the install instructions.
I found that the best way is to download and unzip the avrdude files to a folder. Then download the firmware v2.1.7 (latest and last for OS v2.0 hardware) hex file and place this in that same folder where all of the unzipped avrdude files are located. Verify that that hex file is indeed within this folder with all of the other files before proceeding to the next step.
Now, you need to launch PowerShell which is easiest down by holding the shift key down and (while in the folder you just moved the firmware file) right click this explorer window and select “Open PowerShell window here” which will bring up a PowerShell window that is already pointed to the proper directory.
Here is the next important change that was made from the posted instructions. In the instructions it states to type in the following code (cut and paste works for all of these BTW) and run it:
avrdude.exe -c usbtiny -p m644 -U flash:w:firmware2.1.7.hex
I can tell you that that likely will not work. The problem appears to be twofold. Up first, the avrdude program/application you need to run is just named avrdude w/o the extension on the end. This may work or it may not so try it like this first:
avrdude -c usbtiny -p m644 -U flash:w:firmware2.1.7.hex
Note that the ONLY difference in that string of text is the omission of “.exe”
If that doesn’t work PowerShell will likely give you a hint on how to fix it so that it runs properly. This is to add a “.\” to the very front of the string of text which will then run the avrdude executable which will then complete all of the last steps for you automagically. You should see it erasing and writing the firmware files to the OS.
Viola! All is well and my OS v2.0 now has the most recent and final firmware created for it. Mine has been running about 8 years now and my needs are minimal so there’s no reason for me to throw this in the landfill to get the latest greatest when this meets all of my needs. I only wish the firmware update was a little more beginner friendly but I guess I never need to worry about that again now so water under the bridge I suppose.