How can I enable backspace to go back in Safari on Mojave? There are other questions and answers about how to enable the key Backspace to go back to the previous page in Safari, but none of them work on my newly installed Mojave even though it used to work on High Sierra.

How can I enable this behaviour in Mojave?
You can add a keyboard shortcut from the terminal, but this requires you to disable system integrity in macOS 10.14 Mojave and later.
defaults write com.apple.Safari NSUserKeyEquivalents -dict-add Back &quot;\U232b&quot;


Alternative, you can install a Safari Extension which injects a script that bring back the functionality:
https://github.com/yene/Safari-Backspace
For example:
document.addEventListener(&quot;DOMContentLoaded&quot;, function(event) {
    function handleBackspace(e) {
        if (e.keyCode === 8 &amp;&amp; !e.ctrlKey &amp;&amp; !e.shiftKey
            &amp;&amp; e.target.tagName !== 'INPUT' &amp;&amp; e.target.tagName !== 'TEXTAREA'
            &amp;&amp; e.target.contentEditable !== 'true' // TinyMCE
            ) {
            e.preventDefault();
            window.history.go(-1);
        }
    }
    window.addEventListener('keydown', handleBackspace, false);
});