How can I re-enable backspace navigation in Chrome?

It isn't working for you because, confusingly, it isn't Alt + Backspace, it's actually Alt + ← (the left arrow key).

Google has now published an official extension: 'Go Back With Backspace', to re-enable the backspace button as the hotkey for 'back'.

Re-enables the backspace key as a back navigation button (except when writing text). Go back with the backspace button! This extension re-enables the backspace key as a back navigation button -- except if you're writing text.

Before Chrome 52, the backspace key navigated back (if you weren't writing text). Many people lost their progress while working online by accidentally pressing backspace and leaving a page -- so we removed the feature from Chrome, and created this extension for those who prefer the old behavior.

This extension can't restore backspace on certain special pages, for example any of the "chrome://" pages such as Settings or Extensions.

About the "all sites" permission: In order to capture backspace on every page, the extension needs to install a little piece of code on each one. It does nothing else with the the page, its information, or your typing.

Source: https://bugs.chromium.org/p/chromium/issues/detail?id=608016

If you want to maintain the old shortcut without adding an extension, add this CLI command to your Google Chrome link (right-click shortcut > Properties > "Target"):

--enable-blink-features=BackspaceDefaultHandler --test-type

So in my case, the target becomes:

"C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" --enable-blink-features=BackspaceDefaultHandler --test-type

Credit to Mattias