To works with Tailwind CSS and Tailwind Typography some changes must be done to CKEditor config under "Limit allowed HTML tags and correct faulty HTML" like removing h5 and h6
tags.
Here under you have the defaults values on a fresh install of Drupal for the CKEditor option of "Limit allowed HTML tags and correct faulty HTML".
// admin/config/content/formats/manage/full_html
// "Limit allowed HTML tags and correct faulty HTML"
<em> <strong> <cite> <blockquote cite> <code> <ul type> <ol type start> <li> <dl> <dt> <dd> <h2 id> <h3 id> <h4 id> <h5 id> <h6 id> <s> <sup> <sub> <a href hreflang class="btn btn-primary btn-light btn-info btn-success btn-warning btn-danger btn-inverse"> <img src alt data-entity-type data-entity-uuid data-align data-caption> <table> <caption> <tbody> <thead> <tfoot> <th> <td> <tr> <p> <h1> <pre> <u> <div class="alert alert-error alert-success alert-info"> <span class="text-warning strong text-error text-primary text-secondary text-success text-danger dropcap">
// admin/config/content/formats/manage/basic_html
// "Limit allowed HTML tags and correct faulty HTML"
<a href hreflang> <em> <strong> <cite> <blockquote cite> <code> <ul type> <ol type start> <li> <dl> <dt> <dd> <h2 id> <h3 id> <h4 id> <h5 id> <h6 id> <p> <br> <span> <img src alt data-entity-type data-entity-uuid data-align data-caption width height>