Get InnerBlocks HTML for dynamic rendering of wrapper

Hello, I’m new to WordPress and I’m making my own plugins to add functionality to it. I’m wondering what would be the recommended way of doing the following:

I have a custom block MYPANEL. This custom block works just like a div with a default class and I can put whatever I want inside of it. The point of the custom block MYPANEL is that if later I want to change the HTML of MYPANEL I can do it from the PHP side.

For example, say today MYPANEL is a div with a CSS class that gives it a black border. But in 3 months I decide to redesign MYPANEL and my new design needs a wrapper div to work for some reason, or 3 divs, or I want to use <figure> instead of div, etc. I want to be able to just change the PHP template instead of having to update every post.

<!-- fallback static HTML generated by javascript -->
<div class="my-panel">
  <!-- innerblocks... -->
</div>

<!-- future HTML generated by PHP one day maybe -->
<aside class="my-panel">>
  <div class="my-panel_icon" />
  <div class="my-panel__inner">
    <!-- innerblocks... -->
  </div>
</aside>

Right now, on save in javascript, I return a div with the attributes I take from useBlockProps.save and InnerBlocks.Content as child. This saves in the post’s content an unchanging div. So now I need the PHP template to replace that div with whatever HTML I want, while keeping the inner blocks.

I couldn’t find documentation on what the arguments passed to render_callback?are, but from my debugging I get the block attributes as first argument, some HTML as second argument ($content), and the block instance as the third. I don’t know if the $content is the HTML that was saved from Javascript or HTML generated in PHP that includes dynamic rendering of inner blocks. Either way, there doesn’t seem to be an $innerBlocksHTML argument anywhere. So what’s the appropriate way of getting it?

Should I write a simple regex to remove the outer div from $content? This feels like it could get messy if I ever change the save function in javascript.

Should I iterate the inner blocks and call render_block on every inner block to get their HTML and just concatenate that? Although this probably should work, if $content contains the rendered blocks already, I’m calling all the rendering callbacks of the inner blocks a second time. I think there was an argument called skip_inner_blocks that looked like it made WP skip rendering the $content, but I couldn’t find any documentation on it. Is that what it is for? Is there something like a skip_outer_block setting so I can take just the inner blocks’ content?

What’s the recommended way of doing this?