you're not supposed to be allowed to do this: https://support.google.com/drive/answer/2494892
who knows why; it seems like a common thing even businesses would hit: start with Gmail accounts because non tech and then get a domain and gsuite.
however, there's an interesting qualification:
If you send an ownership transfer request to a personal account and that account becomes a work or school account, the pending owner can’t accept the request.
becomes, you say? That's interesting because transfers work inside organisations. And there's even tooling to move all files owned by a departing user to another account. So..... what's that about?
Plan: transfer the files to the domain consumer account then claim it?
AHA. So you can make a consumer account on the domain then claim it with the domain. Unhinged but worth a try. So I'm going to try it.