As you rightly say, you can use any client for Element Home and the only restriction is that the in-app setup and migration wizard is only available in the Element web clients at the moment (this is now corrected in the blog article).
That said, the Matrix->Matrix migration tools (https://ems.element.io/tools/matrix-migration) can be used outside of the setup flow, to help migrate your existing chats to new accounts. So people can always use those separately from host setup, if needed.
That said, the Matrix->Matrix migration tools (https://ems.element.io/tools/matrix-migration) can be used outside of the setup flow, to help migrate your existing chats to new accounts. So people can always use those separately from host setup, if needed.