From the "it really shouldn't be this difficult - or am I just being dense" file...

I have an Amazon account (actually, I have several because Amazon is weird...) that I am using for Prime Video.  I have several Alexa devices which I previously had used on a different Amazon account, but which I have now reset and will be using them on my Prime Video Amazon account.  I'll be using them around our house to do voice control over our smart lights (using Emulated Hue in Home Assistant), and to provide general access to Spotify, general voice queries, and to add things to a shared shopping list.

But here's where it gets a little tricky.  I'd like to have the shopping list accessible on both my and my partner's phone so that either of us can see what has been added and when we're at the supermarket we can get what is needed.  But I can't see a straightforward way to achieve this.

Amazon seems to be incredibly convoluted when it comes to accounts.  There is a feature called Amazon Family which seems to have replaced Amazon Household - I can link an account for sharing content (e.g. Kindle/Audible and Amazon Prime) but when I try to link my partner's account to mine it says we're in different countries of residence/preferred marketplace.  When I check those, however, we're both showing in NZ.  All I want to do is be able to set it up so that we both see the same shopping list whenever we add something via Alexa.  Can anyone suggest a path through the "fog of war" that is Amazon's settings page?