First off - thank you so much for your suggestions! I’ve been asking around a few different places and was getting basically nowhere (including from manufacturers) and I really appreciate your answer.
I had some amount of success adding the TLV dataset (I had to run this script How to configure preferred Thread network - #53 by Veldkornet) which allowed me to configure this as my preferred network (there’s also a button to “use for ios credentials” it looks like?)
However, when I go into the home assistant app, it asks me to pass credentials - and then fails. Strange! Any thoughts on what to try next?