The output via HDMI is upside down (i.e. flipped).
What I've tried to fix it:
I've tried changing the settings so that the second monitor extends the first, duplicates it, or is the only one - and nothing fixes it.
I've changed the display orientation - I've tried it in "Landscape", "Landscape (Flipped)" and in both portrait modes - and it stays upside down (it doesn't even become portrait when I tried portrait)
I've tried folding the screen back on itself, turning the laptop upside down, etc. - it rearranges the windows as though it's about to change orientation, then reverts to how it was before.
I've tried CTRL+ALT+up, CTRL+ALT+DOWN, etc. - these had no effect at all.
I've tried rotation lock (it's greyed out and locked at "on")
The TV I'm using as output appears to have no settings for changing the orientation of inputs, so this doesn't appear to be a problem at that end.
I'd be grateful for any help - I'm at my wits' end.