> - does hitting 'esc' once instead of Alt+F6/Alt+F7 fix the issue?
That shows a non-themed password promt without problems.
> - does hiting 'esc' *twice* fix the issue?
Sort of, that shows plymouth but the screen is very distorted.
> - does hitting Alt+F7 *without* hitting Alt+F6 fix the issue?
No, the screen remains black.
> - what do you see if you boot without the 'quiet' option (but still with the 'splash' option)?
That doesn't seem to change much but I can't read the text on the plymouth screen anyway.
> - does hitting 'esc' once instead of Alt+F6/Alt+F7 fix the issue?
That shows a non-themed password promt without problems.
> - does hiting 'esc' *twice* fix the issue?
Sort of, that shows plymouth but the screen is very distorted.
> - does hitting Alt+F7 *without* hitting Alt+F6 fix the issue?
No, the screen remains black.
> - what do you see if you boot without the 'quiet' option (but still with the 'splash' option)?
That doesn't seem to change much but I can't read the text on the plymouth screen anyway.