https://www.instagram.com/help/support/privacy and click away the login box with the link at the bottom. I haven't tried it myself, so I don't know if it will work.
On the website select "Yes" -> "How can I get support for a privacy issue from the Data Protection Officer?" -> Click the link at the bottom named "Create Ticket" or similar.
-Meredith Whittaker (Signal President)
https://techcrunch.com/2024/03/04/signals-meredith-whittaker-scorns-anti-encryption-efforts-as-parochial-magical-thinking/
So no interoperability in the near future for Signal.