As of .NET 7, the RijndaelManaged class is obsolete and not recommended. The replacement class, AesManaged is backward-compatible with the old class in that messages encrypted with RijdaelManaged can be decrypted by AesManaged and vice versa.
AesEncryptionService
NServiceBus. version 3.1 includes the AesEncryptionService class that replaces the deprecated RijndaelEncryptionService. In most cases, upgrading involves replacing all instances of RijndaelEncryptionService with AesEncryptionService. No further code changes are necessary.