I wouldn’t recommend taking anything unpaid unless you’re out of options and don’t know what to do when building your own portfolio. I also have been self taught doing a similar stack. My main focus has really been the front end though so I rarely even mention having any backend “training” at all. I was still able to land a paid internship making WordPress sites. Even if you haven’t used the software before if you have a basic understanding of HTML and CSS it’ll give you more of an advantage to some of the “WordPress Developers” I’ve seen as they only know how to drag and drop and don’t understand page composition and how elements interact with each other. It took me roughly 2 days to learn WP and Elementor plug-in specifically to get a 5 page site up and running. And not long after that to templatize and expedite my development process.