I don't think preact is part of the "progressive enhance html"
Progressive enhance HTML means whatever backend you use, it spits out html, and the HTML is rendered without Javascript. Preact fails this.
The libraries are meant to progressively enhance html by replacing or enhancing certain actions with small javascript. For example, with htmx, usually clicking on html link would load complete page, but with clever htmx directive, the link onclick will only load/replace what is needed.
Think of progressive enhance html as html first. As the page working even if javascript is disabled.
