BookStack root URI page search via theme functions file

functions.php

<?php

use BookStack\Entities\Models\Page;
use BookStack\Theming\ThemeEvents;
use BookStack\Facades\Theme;
use Illuminate\Http\Request;

// This will be the content of the functions.php file you'll have
// after following the getting started instructions here:
// https://github.com/BookStackApp/BookStack/blob/release/dev/docs/logical-theme-system.md

Theme::listen(ThemeEvents::WEB_MIDDLEWARE_AFTER, function (Request $request, $response) {
    // Ignore if not 404 or a GET response.
    if ($response->getStatusCode() !== 404 && $request->getMethod() !== 'GET') {
        return $response;
    }

    // Get a path and ignore if more than one path segment.
    $path = $request->decodedPath();
    if (str_contains('/', $path)) {
        return $response;
    }

    // Find a matching page and redirect to that if existing
    // otherwise return the default response.
    $page = Page::visible()->where('name', '=', $path)->first();
    return $page ? redirect($page->getUrl()) : $response;
});