EDIT: I misread. I don't know what an Amazon assistant is. I'm talking about an Amazon echo below

I have one at a cabin in the mountains that has no internet or cell service. It required internet access to sync/auth with my phone so I did it at home then moved it to the cabin. I think it needed to be auth'd to an Amazon account, despite never planning or wanting to use it with an account. It was a "prize" from work.

It is literally impossible for it to connect to the internet at its location but it is a pretty good speaker. Perhaps the loneliest IoT device ever, but I'd never use it in a connected state.

If you only want it for a speaker, you could wall it off to prevent Internet access even at home

I had a google thing which I used as a speaker for a bit. If it has Bluetooth, you could just not let it connect to the internet? As an assistant I found it useless, even without privacy concerns, but as a speaker it was alright.

It's nice that you are trying to find a use for it though! Hopefully it works out long term and you could talk about it the privacy stuff before you get a Facebook Portal next

Fast search gave me this ,replacing with open source firmware Mycroft https://hackaday.com/2021/03/22/amazon-echo-gets-open-source-brain-transplant/