It's just generate a link on Amber and paste on Jumble. But I think if Jumble show a Qrcode to be scanned by Amber app, would be easier to people understand hoe to login.
Discussion
*how
On Amber, the Qrcode say if web app provide Nostr Connect Qr to login.
Nostrconnect is indeed more convenient, but nostr-tools (the tool used by Jumble) seems not to support it, so I need to arrange another time for development.