The D-Link 882 software is unreliable, with frequent disconnects and issues connecting an Xbox One. Switching to DD-WRT firmware failed multiple times and was time-consuming. Here are the steps I used to fix it:
Boot into recovery mode by powering on the router while holding the reset button.
Set your computer's wired connection to a static IP (e.g., 192.168.0.3) and disconnect other hardwired devices.
Access 192.168.0.1 using a browser like Canary or Chrome
10.0.01 pause time.
Select the factory to DD-WRT file for flashing but do not upload it yet.
Keep the web browser open with the file selected, turn off the router.
Turn on the router while holding the reset button to enter recovery mode again.
Wait for two minutes for the router to boot into recovery mode, then hit upload in the web browser.
Allow the flashing process to complete without interruption. The router should automatically reboot. If not, wait an additional 5 minutes.
Set your computer to obtain an IP address automatically, then navigate to 192.168.1.1 to access the DD-WRT screen.
You can now update DD-WRT using the webflash. I recommend using DD-WRT v3.0-r37305 std (10/10/18), which has been stable for me.