When creating an integration today you can select the region in which your AWS bucket resides in. This option seems to prevent the storage_only (customer filter flow) integrations from being created correctly.

This leads to the following error:

WARNING 07290d25-72fa-429a-b50d-423931a41a0f 680 Unable to download manifest for provider: d799a59d-5d24-494f-b6a5-48a5add4d97f. Error: An error occurred (InvalidClientTokenId) when calling the AssumeRole operation: The security token included in the request is invalid..

Side note, running without specifying the region results in:

botocore.exceptions.ClientError: An error occurred (IllegalLocationConstraintException) when calling the GetObject operation: The {region} location constraint is incompatible for the region specific endpoint this request was sent to.