LiveCanvas is a WordPress page editor that lets you build WordPress content using vanilla CSS, Bootstrap 5, or Tailwind. It is different from other page builders as it includes an advanced HTML editor and saves the pages you create with it as HTML, so that there is only clean code. You can insert shortcodes from other plugins. LiveCanvas requires some HTML and CSS knowledge to use effectively, but is an alternative for people who don’t like traditional page builders. It allows you to create theme templates, including ones for Custom Post Types. You integrate custom fields via their shortcodes or PHP functions or you can use the Loops and Logic syntax, which has recently been integrated.
The team has a custom Picostrap5 Bootstrap 5 theme that includes a number of Bootstrap UI components.