Always verify you are downloading the "H/W Ver A3" file. Using a file meant for A1 or A2 will result in a failed update.
The DIR-853 A3 is widely supported by the OpenWrt Project , offering more advanced features than the stock firmware. dir853 et a3 firmware update link
To update the firmware on your D-Link DIR-853 (ET) Revision A3 Always verify you are downloading the "H/W Ver A3" file
She uploaded the firmware image through the router’s web interface and watched the progress bar. Midway, the power flickered; Mei held her breath. The router rebooted, LED lights cycled—then settled. She logged in, restored the configuration from backup, and ran a quick connectivity test: multiple devices streamed video, VoIP calls stayed clear, and speed tests matched expectations. the power flickered