Serve a page on its own domain in Kirby 2

I am sorry if this has been asked before.
I have only been able to find solutions for Kirby 3 and I am unsure whether any of those could work for Kirby 2 as well.

I’d like to have a subdomain render a page / specific content folder for a kirby 2 project.

Essentially have display what would normally be on
and have redirect to

Is there a way to make it work automatically for all subdirectories of

So that if I ever decide to create a, it would also redirect to without my doing anything else and have render what would normally be displayed on

The redirection from a subdirectory to the subdomain is done via htaccess, as far as I can tell.

My idea was that I might be able to do that via server or DNS settings in some way,
but unfortunately I don’t have that kind of access to my customer’s server.

Not with DNS but either server settings or in .htaccess of you could redirect sub/(*) to $