I don’t think there’s an endpoint that will give you all group members with their bio. You’ll need to loop through the users to get their bio. You can get group users from something like https://meta.discourse.org/groups/support-experts/members.json?offset=0&order=&asc=true&filter=
Profile - pfaffman - Discourse Meta shows my bio in an incognito window, so the bio might be available on your site to anonymous users, so you wouldn’t need an API key.
Maybe you want to look at Reverse engineer the Discourse API
I was once an academic. My wife does discourse analysis with tools like ATLAS.ti and I’ve spent some time pulling data from various sources to be analzed with various tools. Good luck to you!