Paths specified in yesod and APPROOT are not reflected in routing

The Yesod application configures the following:

config/routes

/HomeR GET POST

config/settings.yml

 host:"_env:HOST:*4"#any IPv4 host
port: "_env:PORT:3000"
approot: "_env:APPROOT:somedir/"

Accessing "http://localhost:3000/somedir/" in this state does not call the HomeR handler. How do I get the yesod application to move under a specific path?

add
There was a proposal to use reverse proxy.
In Apache's mod_proxy, set it as follows:

Redirect/somedir/somedir/
ProxyPass/somedir/http://localhost:3000/

You can now access HomeR by accessing http://localhost/somedir/.However, the URL deployed in the template does not have /somedir/, which causes the CSS and all links to fail.

For example, write a template similar to the following:

<a href="@{HomeR}">Home</a>

It is deployed to <a href="http://localhost:3000/">Home</a>.<a href="/">Home</a> when using ApprootRelative.This will not make the site work.

In order to avoid this, I think it is appropriate to inject somedir when interpreting config/routes.However, projects using the stack template do not write that mkYesodData starts when you build a route by specifying the directory of the application route in the environment variable, not when you read the environment variable.

I'm studying whether to build a route without using mkYesodData or implement something equivalent to mkYesodData