How to remove H1 title from CMS pages and category pages in Magento 2

For removing the tittle from the home page you can just add <referenceBlock name="page.main.title" display="false"/> in your cms_index_index.xml. You can also use display true and false from where you want.

If you just go into the admin and go to content > pages and click edit on home page (or any page), there is a section called design where you can paste in the xml you want to execute. In this case, if you add: <referenceBlock name="page.main.title" remove="true" />

It will remove the title from the home page.

Seeing as still nobody's posted what to edit for category pages, the XML file to edit is in /vendor/magento/module-catalog/view/frontend/layout/catalog_category_view.xml. The block to edit is pretty much the same as for CMS pages:

<referenceBlock name="page.main.title" display="false">