Yes, you can file RTI application to sub registrar office in Karnataka for all the relevant matters which falls in the jurisdiction of the Sub Registrar. It comes under the Karnataka Revenue Department. Mainly the sub registrar offices are responsible for the maintenance of records of all property documents that are registered. Once registered, such documents become a public document. They are regulated by the guidelines of the Registration Act (Central Act No XVI OF 1908) PART XI. Hence, it is a public authority under section 2(h) of the RTI Act 2005 and application can be filed under section 2(f) and 6(1) after payment of requisite fees.
To know further please refer https://onlinerti.com/how-to-file-rti-online-for-karnataka