Need advice for running React app on linux server
Solution 1:
For starters, a "site" in sites-enabled is actually a virtual host, so if you want to make your new application available under a path in an existing virtual host, you'll need to modify the configuration for that virtual host's server block, rather than create a separate configuration file in sites-available.
From there, it's a relatively straightforward HTTP reverse proxy configuration, as per the fine manual.