Is it possible to force the next boot to be a recovery mode boot with a bluetooth keyboard?
This model seems to respect the option key only - so that will get me to the startup manager and I can select the Recovery HD.
I have not had luck getting command R to work but it's clearly meant to work as well - perhaps that's for newer macs with better bluetooth hardware (or my mac is just cranky and not working as designed)
At least, on macbook pros (10.9 -> 10.14.6) you can run the command
sudo nvram recovery-boot-mode=unused
And the macbook pro will boot into recovery when you restart, the flag will be removed from nvram so you boot normal the next time after it.