Hello MF
You can override your components or whatever inside the HTML folder as before. We've just introduced a new system of overriding for the users so that the user's changes don't lose after the template update.
For example, we've created a template named xyz. You are now using the template. But you want to change one of the overrides of the com_content's file.
Now normally what will you do? You go to templates/xyz/html/com_content/the_file_name.php file and change that file, right?
After a few weeks, we've released a new version of the template v2 and you've updated to the new version, and you've noticed that the changes you've made before have gone. This is not what you are desiring.
For solving this problem, we've introduced a new system. In the new system, you have to write the only line of code at templates/xyz/html/com_content/the_file_name.php is -
require HelixUltimate\Framework\Platform\HTMLOverride::loadTemplate();
and then go to templates/xyz/overrides/com_content/the_file_name.php and write your code there. And now if you update to the version v2 you will not lose your changes.
I hope, now you can understand the situation. Let me know if you have any further queries.
Best regards