It took me about five years to get Revolut to return to me the funds in an account I could no longer access (Revolut overnight upped the Android requirement for their app, so I could no longer access), where they had no mechanism by which to regain access.

In the end I managed it by issuing a GDPR. Revolut's GDPR staff were able to finally shut the account, and send me the funds, so I got them back.