Info extracted from https://sushantbhosale.com/install-dd-wrt-d-link-dir-882/
Text in ORANGE is differences noted from original document.
Download the Flash Files
Go to http://dd-wrt.com and click
Router Database. Search for "D-Link DIR-882".
You need to download two files. First download the "factory-to-ddwrt.bin" file and the dlink-dir882-a1-webflash.bin file. The file version changes, so download the latest file. My date for the file shows 2018-10-10.
Enter Flash Mode
Now for the fun part. It's not easy as press upload on the router GUI and flashing DD-WRT firmware on the router, so you need to put your router in crash recovery mode to install the new firmware.You cannot do this via the d-link provided UI.
Reset to Recovery Mode - Press and hold the reset button on the router. While keeping that pressed, pull the power cable out and insert it back after 5-10 seconds.Now let go of the reset button. Wait for about a minute or two and you will see the LEDs blinking ORANGE.
Assign your computer an IP address of 192.168.0.2 manually. You have to do this by going in the network settings and setting it as ‘manual’. Connect a network cable from your LAN port on the router to the Ethernet port on computer.
Connect PC/Mac to
Now open your browser and goto http://192.168.0.1. This is the IP of your router and 192.168.0.2 is the IP of your computer. This makes it easy for your computer to talk to the router directly through wired connection. The D-Link recovery page should display now. In case you don’t see it, then the recovery mode failed and you will have to repeat the above steps again.
Install Factory-to-ddwrt Bin File
Browse to factory-to-ddwrt.bin file and select. Do not press Upload button just yet. You should now repeat step 4 above to reset router again (Thanks Lee Bowie). Usually takes about 5-10 mins.
Install full DD-WRT
Once the process finishes uploading, remove the manual address on your computer, set it to DHCP or your regular method to obtain IP address to connect to the network.
Goto 192.168.1.1. This is the default IP DD-WRT assigns once it is flashed. You should now see DD-WRT UI. Create a username and password to login.
Now goto Administration > Firmware Upgrade and browse to the "webflash.bin" file. You will have access to pretty awesome settings offered by DD-WRT. Using Firefox works best!