By default a swap is triggered on every htmx request. If you return html from that endpoint, it will be swapped. You said you put code on a div, but if you put it on the actual select element you don't even have to bother with

hx-target

. For example,

html
<!-- form -->
<select hx-trigger="load" hx-get="/get/my/options"></select>

<!-- return from /get/my/options -->
<option>option 1</option>
<option>option 2</option>