Issue is that AS provided GA and GTM code snippets. The GTM container is completely empty, so only the GA pageview is firing. Typically we wouldn't put GA and GTM on the same page, so waiting on clarification.
the last part about using aria-hidden on everything else seems quite complex, skipping that
another issue is that I designed my modal to have any interior content, but setting the focus on the item you want may not work with slots. Will need to test with real content sometime.
Looks like if you have multiple checkboxes hooked up to the same model, with no values, it'll just be a boolean and they'll overwrite each other, if you set a value to a string, they'll populate an array automatically.