I would like to know if there's any hackable way anyone might know of which will allow an HTML datalist element to work with a contenteditable element and not with an <input> element.

Example code:

<label>Choose a browser from this list:
  <span contenteditable list="browsers" name="myBrowser">choose</span> 
</label>
<datalist id="browsers">
  <option value="Chrome">
  <option value="Firefox">
  <option value="Internet Explorer">
  <option value="Opera">
  <option value="Safari">
  <option value="Microsoft Edge">
</datalist>

fiddle demo

It would seem like it is bound to only with with <input> element. In my situation I have javascript plugin which hides an input field and replaces it with a span, for some "special" things that can only be done with a regular DOM element, such as span. This span is contenteditable and acts is a simulation for the input it replaces, while the input is kept hidden.

As far as I'm aware, there is no standard to apply a <datalist> to random elements with the [contenteditable] attribute, or anything other than a input with the [list] attribute. At best, you'd be beholden to how individual browsers choose to implement that spec.

Obviously, the best medicine is to convert to semantically correct html, but just adding that note for future visitors to do if possible, since that's not your use case.

A possible workaround is to spin up an input element during the focusin event, match the styling of the surrounding span, allow the native browser events to fire, and apply the updated value when the input loses focus.

Here's how that would look in JavaScript:

document.addEventListener('focusin', function (event) {
	if (event.target.matches('[contenteditable]')) {
        var editable = event.target
        
        // get text
        var text = editable.innerText

        // create input
        var input = document.createElement("input");
        input.type = "text";
        input.className = "editable-mirror";
        input.setAttribute("list", "browsers");
        input.value = text;

        editable.appendChild(input);

		input.focus()
	}
});
document.addEventListener('focusout', function (event) {
    if (event.target.matches('.editable-mirror')) {
        var input = event.target
        var editable = input.closest("[contenteditable]")

        // get text
        var text = input.value;

        // destroy input
        input.parentNode.removeChild(input);

        // apply value
        editable.innerText = text;
    }
});

And some starter styles (although Your Mileage May Vary)

[contenteditable] {
  position: relative;
  border: 1px solid silver;
  padding: 2px 5px;
  display: inline-block;
}

.editable-mirror {
    position: absolute;
    left: -1px;
    top: -1px;
    height: calc(100% + 2px);
    width: calc(100% + 7px);
    padding: 2px 5px;
    margin: 0;
    border: 0;
}

Here's a working demo in Stack Snippets & JSFiddle

<!-- begin snippet: js hide: true console: true babel: false --> <!-- language: lang-js -->
document.addEventListener('focusin', function (event) {
	if (event.target.matches('[contenteditable]')) {
        console.log('focused')

        var editable = event.target

        // enter edit mode
        editable.classList.add("editing")
        
        // get text
        var text = editable.innerText

        // create input
        var input = document.createElement("input");
        input.type = "text";
        input.className = "editable-mirror";
        input.setAttribute("list", "browsers");
        input.value = text;

        editable.appendChild(input);

        input.focus()
        
	}
}, false);
document.addEventListener('focusout', function (event) {
    if (event.target.matches('.editable-mirror')) {
        console.log('blur')
        
        var input = event.target
        var editable = input.closest("[contenteditable]")

        // leave edit mode
        editable.classList.remove("editing")

        // get text
        var text = input.value;

        // destroy input
        input.parentNode.removeChild(input);

        // apply value
        editable.innerText = text;
    }
}, false);
<!-- language: lang-css -->
[contenteditable] {
  position: relative;
  border: 1px solid silver;
  padding: 2px 5px;
}

.editable-mirror {
    position: absolute;
    left: -1px;
    top: -1px;
    height: calc(100% + 2px);
    width: calc(100% + 12px);
    padding: 2px 5px;
    margin: 0;
    border: 0;
    font: inherit;
}
<!-- language: lang-html -->
<h2>Regular - Input + Datalist</h2>
<label>Choose a browser from this list:
<input type="text" list="browsers" placeholder="Edit Me" id="regular" /></label>

<datalist id="browsers">
  <option value="Chrome"/>
  <option value="Firefox"/>
  <option value="Internet Explorer"/>
  <option value="Opera"/>
  <option value="Safari"/>
  <option value="Microsoft Edge"/>
</datalist>

<h2>Workaround - ContentEditable + Datalist</h2>

<label>Choose a browser from this list:
<span contenteditable list="browsers" name="myBrowser">edit me</span></label>
<!-- end snippet -->