So every few months now, blue triangle of death where I know now no matter what I do, eventually the only way is full hard reset / reformat which upsets me to no end.
This time though it dawned on me to try the various undocumented modes.
To my surprise there is one that seems to activate, the undocumented "preboot" mode (the service menu mode does not work).
Basically you power off, hold the START key (upper right) and then while keep holding, plug in the USB cable. Never let go of that start key or mode ends.
This makes windows see the Fenix as the preliminary "garmin gps" in the device tree and shows connected on a USB list.
However this does not assign it a drive letter, which means files on the flash storage on the watch cannot be seen by windows natively.
The old never-mentioned Garmin WebUpdater will see the device, and even Garmin Express sees the device but it does not see it as the old existing Fenix, it sees it as an unknown serial number 0 (zero)
Supposedly it is possible to write RGN files (firmware) to the device in this mode.
So given that, is there any chance in heck to copy files off the device?
Probably should ask this in the developer sub-forms but starting the thread here just in case someone comes across it in the future and knows the answer.