What do the Dell diagnostics reveal (F12 at powerup)?

When I do this it says "no bootable device found"

After pressing F12 it says: Operating System Loader has no signature. Incompatible with SecureBoot. All bootable devices failed Secure Boot verification.

My only available option is to Shutdown

Turn secure boot off - then retry.

There is another thread where someone where someone explains how to add a workaround boot option to use another Boot Manger to get your system running.  If you can find it, try it out to see if it works since is has for some others.

It says "No bootable devices found"