OK, I have found a semi-solution to this.
```
sudo apt install wlr-randr
```
Then edit ~/.bashrc and add this:
```
function flip() { wlr-randr --output DSI-1 --transform 180; }
```
Then `. ~/.bashrc` to reload bash. Now, when you run `flip` either on the phone's terminal or over SSH, You'll be in upside-down portrait mode.
This is nice because you can dock your phone and keep it plugged in, and the headphone position is like an old iPod touch (if you like that).
However, you can't flip it this way using the indicator. It will flip back to normal portait mode if you click it, then landscape. These are the three things I would like to do:
- Make the upside-down portrait orientation permanent;
- Make it work with the phosh indicator;
- Invert the volume buttons so they're also upside-down.