How to make a constructor template the main page, and leave Bitrix alone to do everything else?

Question

1C-Bitrix

GIVEN. Site on Bitrix... the pages seem to be made with the help of internal templating, tk. there are only directories and blocks, as well as a certain template in the templates section.
And there is also a Landing page created in the same section using the constructor proposed by Bitrix...

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And now attention to the task!
It is necessary to make this Landing the main page, while not touching the templating and content of the rest! (at the same time, it is not necessary to leave the Landing itself exactly in the section of this site, if there is actually a solution, let’s make a Design Template for the main one from another “Site” entity, then it’s not a question at all, in general, any solution will do, but the main condition, the Design Template = Home, other pages unchanged!)

P.S.
To make it clearer what is at stake, here is a screenshot

Answer 1

1. Remove the index.php file from the site root (just rename it for now)
2. Settings->Modules->Sites24 - there is "Publishing paths relative to the site root", by default there is something like /lp/, just leave / and set up the rest as you need
3. Settings->Sites->List of sites, go to your site, at the very bottom of the "Site template", an entry should appear, approximately Landing24 (maybe another name) and in the conditions it says Add index.php 4. Publish the page through the Sites24 interface, after that a new index.php with the bitrix:landing.pub component should appear in the root PS Be sure to make a backup, there are anomalies with these Sites24)
CSite::inDir('/')
CSite::inDir('/index.php')