Does it require installing 3rd party software on the host machine? This might not work great for this kind of "shadow IT" application in all environments, whereas one that acts as a USB keyboard might be more versatile.

Does it require installing 3rd party software on the host machine?

No, it identifies as a keyboard. It also defaults to generating a password that will use the same scancodes on (most?) western keyboard layouts so that computers configured to default to e.g. QWERTZ or AZERTY will still result in the same password.

How do you tell it which password to type?

IIRC there is a maximum of two; one on short-press and one on long-press.

Only to configure it. It presents as a USB keyboard (among other device types).

How do you tell it which password to type? I haven't seen yubikeys with physical interfaces to select a particular password.

I should do this for ssh password entry. Running ssh-agent is still 90% of the story, but it comes up often enough that I'm on a terminal in a remote machine or inside a screen session or something that it would still be awfully useful to be able to just autotype it.