DISCLAIMER: So this is one of those "I'm not quite sure how I finally figured it out" solutions, so hopefully I am writing this up the way I actually did it that also got it to actually work. As usual I'll include my source sites at the bottom. Apologies for example screenshots & photos not being available for every step!
**This required use of Apple Configurator 2 app on a Mac, and potentially an Apple Developer account to access additional original tvOS files. I was not able to fix this using Xcode but I was able to help validate it was fixed using Xcode. EasyFind app is also quite helpful in this case.**
EQUIPMENT: A Mac Computer, and a cable of type USB-A to USB-C (or possibly USB-C to USB-C cable) is what was successful in my case. A Belkin Thunderbolt 3 to Thunderbolt 3 cable would also suffice. Note: the Mac being used only had USB-C ports, so I needed a USB-A to USB-C adapter to connect the AppleTV back to my Mac...
The Problem - an AppleTV HD (aka 4th gen.) had a rapidly flashing LED light at power on and showed no video. Upon connecting the AppleTV to a Mac computer, Finder showed that the AppleTV needed to be "restored" and prompted me to do so. It did not give me an option to specify the restore file like some of the articles online indicated, but had one button and one button only that said Restore; it would proceed to download "the most up to date tvOS restore file", but ultimately the restore effort would fail with an error:
"tvOS cannot be restored on this device. - The System restore image is invalid. [ConfigurationUtilityKit.error - 0x2BD (701)]"
Turned out whatever file it was looking to or supposedly downloading from Apple online and then looking to as its restore file was corrupt.
Also to complicate matters, Apple Configurator 2 showed the device was not "booted".
The Solution - Using EasyFind, search for "Only Files, All Words, Invisible Files &
Folders" for .ipsw (no * wildcard) in your local user username profile
folder. Making note of the file and folder names, locations and timestamps, then move any existing .ipsw files in the ACUDownloadFileOperation folder and or in any subfolders out to the Desktop.
Next, in Apple Configurator, go to the menu bar dropdown menu and select:
"Actions" -> "Advanced" -> "Revive Device."
Once the "revive" process finishes, my AppleTV showed it was in state "booted" with the seemingly appropriate tvOS version based on the EasyFind search I mention next. The LED was still rapidly flashing and the Apple TV was still showing as needing to be Restored / in Restore mode but was now "booted".
Go back to EasyFind and rerun the search with the same criteria. There should a new instance of the .ipsw file with a new timestamp. Select to highlight the file and choose Reveal in Finder option button in EasyFind.
Back in Apple Configurator app, drag the .ipsw file from Finder to the Apple TV device's Info tab - I believe it was the only tab that would allow me to drag and drop the file to - this should then initiate a Restore and install of tvOS with the freshly downloaded file.
The AppleTV needed one more thing to be able to be finished apparently and that involved steps usually reserved for company deployment. But it worked - so click Prepare button in the window menu of Apple Configurator. The options I used were as follows on the screenshots -
1) Manual Configuration, Supervise devices, Allow devices to pair with other computers
2) Do not enroll in MDM
4) Input any info for organization information
6) Show all steps with all checkboxes checked
Then authenticate with your Mac login creds to allow making changes to your Certificate Trust Settings.
AppleTV will then restart and display in Apple Configurator with the AppleTV app screen on the preview image, show the about and tech spec info, as well as an Organization section.
If you have issues with the file being automatically downloaded, you can try downloading the latest restore file on the Apple Developer website to then drag and drop to the Apple Configurator window - currently there is a file compatible with the AppleTV HD (ie 4th gen.) and above, filename AppleTV5,3_14.2_18K57_Restore.ipsw: https://developer.apple.com/download/release/
Sources:
"Revive an iPhone, iPade, or Apple TV in Apple Configurator 2": https://support.apple.com/guide/apple-configurator-2/revive-an-iphone-ipad-or-apple-tv-cad367dc4593/mac
"Restore Your AppleTV": https://support.apple.com/en-us/HT203028
"The software was corrupted during download": https://discussions.apple.com/thread/250953112
"If you can't update or restore your iPhone, iPade or iPod touch - Apple Support: https://support.apple.com/en-us/HT201263
"Identify your AppleTV Model": https://support.apple.com/en-us/HT200008
"Apple Configurator error code - MDKZipUtilitiesErrorDomain error 1" (Shout out to Bruce4051's post from Oct. 3, 2013!): https://community.spiceworks.com/topic/385692-apple-configurator-error-code-mdkziputilitieserrordomain-error-1