This release fixes bugs in the previous 3.6.x firmwares. See the change list at https://github.com/Duet3D/RepRapFirmware/wiki/Changelog-RRF-3.x-RC#reprapfirmware-363-rc1.
Also included in this release are new firmware files for WiFi modules. See https://github.com/Duet3D/WiFiSocketServerRTOS/releases/tag/v2.3.0-rc.1 for the change list.
Also included in this release are new bootloader files for tool and expansion boards. These bootloaders adapt automatically to CAN bit rates of 1Mbps, 500kbps and 250kbps.