This is basically the same as Make the block title required and allow it to be hidden for D8, but applied to both block titles and layout page titles.
D7 (<none> required to hide title):

D8 (checkbox that toggles visibility of title):

GitHub Issue #:
692
Recent comments
It's great that everyone has a choice. I'm currently making a website where the H1 title is located at the top of the page in full width with a background image, 50vh height, how do you like...
Block title combo and 2/3 things
In the end, I use my <h1> with my custom layout just before the region for the content and i make a preprocess_theme for site_identity. <?php print theme('site_identity'); ?>...
Block title combo and 2/3 things
Choosing to not use the "Page title combo" block on content can also be helpful if you want to arrange the "Page tabs" menu and "Page title" differently.
Block title combo and 2/3 things