Hello,
Regarding the JSON-RPC functionality in the latest firmware, there is no option to enable it via Web UI but there is somehow a workaround to enable it only that it may brick the router so it is suggested to downgrade the firmware to 6.08.3 if you want to use the JSON-RPC. Fixes for this one will be included in the RUTOS 7.2 Firmware. Regarding when it will be released there is no exact time as of now.
Thank you and have a nice day!
Regards,
Mellow