htaccess make urls respond from /index.json as well as / - wordpress

Question

I have a Wordpress site that responds with JSON to every request, i.e. the following pages:
/
/about
/about/team
All respond with json. The htaccess file looks like this:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
I'd like to keep what I have now, but also respond with the same data when index.json is added to the url:
/index.json
/about/index.json
/about/team/index.json
How can I update my htaccess to also respond to these urls in the same way?

Answer 1

Based on what #MrWhite said in comments (gonna quote here, because comments might get removed later),
However, the "problem" here is WordPress. WP routes URLs based on the REQUEST_URI, which does not change during a URL rewrite. So you really need to implement this within WordPress itself.
you could probably just “reset” the value of $_SERVER['REQUEST_URI'] in PHP, if it ends with /index.json. (Relatively easy string manipulation / regex job.)
The remaining problem would just be to figure out a “correct” way to do this – I guess trying to do this via any hooks from inside the theme’s functions.php or a plugin, might be too late. You can give that a try anyway, if you like - the order of hooks as described here is what I would go by, https://wordpress.stackexchange.com/a/162869
The init hook is pretty far down, even after the current user was determined, etc. – but maybe plugins_loaded or setup_theme might be suitable for stuff like this.
If that doesn’t work, still some possible alternatives:
If you can influence the PHP configuration, auto_prepend_file would allow you to specify a script that gets automatically run before anything else PHP does - so you could fix the value before the index.php code even executes.
You could write your own little “wrapper” file, say index2.php, that fixes the value, and then simply includes the original index.php afterwards. Only problem with that - you probably wouldn’t want to change the default WP rewriting between the BEGIN and END WORDPRESS comments in the .htaccess, because WP will overwrite that part, when you flush your permalink settings. But an additional internal rewrite of index.php to index2.php after, could probably solve that.
If mod_proxy is available, you could proxy the request internally. Probably not the best in terms of performance, but at least an alternative to an external rewrite, if you wanted to avoid that at all cost.