wildcard-subdomains | Handle dynamic subdomains in Node.js and Express | Runtime Evironment library

I have a website that uses Apple universal links for sharing app events with others. Opening an event link on a device without the app installed should display a site that lets the user download it, but it should also keep the address the same. Reason for this is that this page will also be shown when the universal link is opened inside an app such as messenger, where it will have a label that asks the user to press "open in safari". Pressing that button must the open the initial link in safari to open the app correctly.

The website looks like this:

www.website.com/event/

The user will then be shown the site:

www.website.com/invite

While keeping the initial link in the address bar.

I need to accomplish this using my .htaccess file, and as I do not host the server myself but rather through a webhosting service, changing any deeper settings is difficult.

I've tried to use RewriteEngine RewriteCond and RewriteRule , by looking at these questions among others without any luck:

I'm using wildcard-subdomains to handle wildcard subdomains in my express app, so something like subdomain.localhost:3000 would enter the router as /s/subdomain/.

I want to match the main index url of any subdomain, but none of the pages under it.

Essentially, I want a route that would match /s/subdomain/ but not /s/subdomain/page/ or /s/subdomain/page (for clarity, "subdomain" is just a placeholder for any wildcard domain)

This is simple to do in regular regex, but I am unable to use the dot modifier due to express using path-to-regexp. It would be possible for me to generate a router for each user, but I would really like to use something cleaner if it's possible.