So I upgraded to Catalina. Actually it's more like a fresh install, I only copied across the few files I wanted to keep.

The shell is now helpfully telling me:

The default interactive shell is now zsh.
To update your account to use zsh, please run `chsh -s /bin/zsh`.
For more details, please visit https://support.apple.com/kb/HT208050.

The information on that page helpfully shows GUI instructions which do not work. Specifically, it says "Control-click your user name in the list of users on the left, then choose Advanced Options.", but Control-click does nothing. So I reported that on the page.

When I use the suggested command instead:

hostname:~ username$ chsh -s /bin/zsh
Changing shell for username.
Password for username: 
chsh: Operation was denied because the current credentials do not have the appropriate privileges.  Operation was denied because the current credentials do not have the appropriate privileges.
chsh: no changes made

This is different to "Can't use zsh shell in Catalina" because I get an error message that they don't.

It's also different to "chsh: Operation was denied because the current credentials do not have the appropriate privileges" because it seems that in their case, they were using iTerm. I'm using the default Terminal.app.

I have tried it with sudo just for laughs, but of course it does this, which makes perfect sense:

hostname:~ username$ sudo chsh -s /bin/zsh
Password: 
Changing shell for root.

So what's the deal here? How am I supposed to do it?

Update:

Well this is interesting. Two password prompts, and then a different error message about the parameter being invalid.

hostname:~ username$ sudo chsh -s /bin/zsh username
Password: 
Changing shell for username.
Password for username: 
chsh: One of the parameters provided was invalid.  One of the parameters provided was invalid.
chsh: no changes made