I'd like to try but don't have a kndle. I think the issue is more about web standards, there's not one yet to define it but all major browsers have that option available when certain tags are available on the page.

The post-type item could be better structured from an HTML5 perspective, as it mostly for long-format contents including the <section> or <article> semantic tags could be one option.

This article from 2018 has some -maybe yet outdated- details for each browser