In T4 framework 2.x you inserted the <main> markup as wrapper element for anything except of the off-canvas sidebar. In version 1.x of the framework it was not the case.
As mentioned here (https://www.w3schools.com/tags/tag_main.asp) the intention is to use it for unique content on the page. And NOT to include code of main navigation, footer, side bars etc.
Your implementation makes it more difficult for blind and visually impaired people the select the main content via screen reader tools that are relying on a correct use of the markup.
It would be great if you could rethink the use of this markup and place it where it makes sense.
Thanks in advance.
Karsten Dietrich