On startup LO tries to recover "Untitled 1". Can not discard or recover or complete startup. How to clear this?

LO version 6, Ubuntu 18.04LTS
LO is unusable until cleared.
The file is not important, it can be deleted.

How exactly does “Can not discard or recover” manifest? Usually clicking Discard leads to a dialog “Are you sure …” where you click Yes and that’s it.

From your brief description I don’t understand exactly what happened. Best I think to try to include the exact wording from the screens. I keep a pad of paper for situations like this where I need to jot something down. Alternatively and often better but not always usable is to have a screen saver installed and know how to take screen snapshots.

This is a program bug – each time the recover screen (showing start or discard) starts the code must clear the choice flag, this is not happening thus the program is trapped in an endless loop.

If clicking Discard for some reason does not work, try hitting the Escape key, which should bypass the dialog. Alternatively start from the terminal command line using soffice --norestore & which also bypasses the dialog. This is only a temporary measure, for both methods when starting LibreOffice normally the next time the recovery dialog will be presented again.

That box appears under a box that has the Untitled showing which is active
and the only choice is “OK”. The box under that, which has the discard choice, is inactive and can not be activated, so is useless. The “OK” choice produces the same routine with the same single “OK” choice over again… No “Are you sure” ever shows up.

ESC just exits and --norestore generates ‘application error’
Fatal exception: Signal 6
Stack: (looks like the system stack is dumped maybe got a core dump also.)

Sounds like your installation has more problems than just this…

Try to invoke soffice --safe-mode & from the command line and choose a fresh user profile. If that doesn’t work either then manually move the old profile out of the way, see LibreOffice user profile - The Document Foundation Wiki

This is a program bug – each time the recover screen (showing start or discard) starts the code must clear the choice flag, this is not happening thus the program is trapped in an endless loop.

The bug still exists but, I got around it by starting LO using safe mode.
Working syntax: $ grun libreoffice --safe-mode