In v5.9.0 (released August 2022), Ghost added native comments.

Native comments are supported in v1.3.0 of the Ali Abdaal theme but if your site is running a previous version, you can add native Ghost comments very easily.

Open post.hbs and go to line 143. You'll see code for Cove comments already in the theme:

{{#if @custom.cove_id}}
<hr>

<h2 class="toc-exclude"><span id="cove-count"></span> {{t "Comments"}}</h2>

{{^if @member}}
  <p><a href="" data-portal="signup">{{t "Sign up"}}</a> {{t "or"}} <a href="" data-portal="signin">{{t "Sign in"}}</a> {{t "to join the conversation."}}<br>
{{/if}}

<div id="cove"></div>

{{#if @member}}
  <p>{{t "Signed in as"}} {{@member.email}} · <a href="#" data-members-signout>{{t "Sign out"}}</a></p>
{{/if}}

<script>
const Cove = {
  contentId: "{{id}}",
  memberId: "{{@member.uuid}}",
  memberEmail: "{{@member.email}}",
  memberName: "{{@member.firstname}}"
}
</script>

{{/if}}

To add native comments, you can remove the code above and replace it with the following:

{{#if @site.comments_enabled}}
    {{#if comments}}
        {{comments}}
    {{/if}}
{{/if}}

This will enable Ghost comments on every post, which looks like this: