Obtaining full HTML of a SPO Site Page programatically

Hi I need to obtain the full HTML of a SPO Site Page programatically.

I have a SPFx web part showing latest published site pages. So far I tried with PNPJS (ClientSidePage.fromFile) with Search (CanvasContent1OWSHTML) and with SP REST API (getbytitle('Site Pages')/Items?$select=CanvasContent1)

All of them seem to return some HTML which is not the full page.