Hello,
I am not sure if this really is a bug but after trying different things over the last few days, googling a lot about it, following different tutorials online I wasn't able to find the reason behind this.

Steps to reproduce the issue

Create a new component and add the following front-end files:

1. Add a DisplayController to the site part with path com_bar/src/Controller/DisplayController.php

namespace Foo\Component\Bar\Site\Controller;

use Joomla\CMS\MVC\Controller\BaseController;

class DisplayController extends BaseController
{
	public function display($cachable = false, $urlparams = []): DisplayController
	{
		return parent::display($cachable, $urlparams);
    }
}

2. Add a View to the site part with path com_bar/src/View/Foo/HtmlView.php

namespace Foo\Component\Bar\Site\View\Foo;

use Joomla\CMS\MVC\View\HtmlView as BaseHtmlView;

class HtmlView extends BaseHtmlView
{
	public function display($template = null)
	{
		parent::display($template);
	}
}

3. Add a template with very basic content to the site part with path: com_bar/tmpl/foo/default.php

default template for foo part

4. Install component (with uninstalling the old one before).
5. Go to URL http://localhost/index.php?option=com_bar&view=foo
6. The error is shown

Component XML:

        <!-- Frond-end files -->
	<files folder="site/com_bar">
		<folder>src</folder>
		<folder>tmpl</folder>
	</files>
	<media folder="site/media" destination="com_bar/site">
		<folder>css</folder>
		<folder>js</folder>
		<folder>img</folder>
	</media>
	<languages>
		<language tag="en-GB">site/language/en-GB/en-GB.com_bar.ini</language>
		<language tag="de-DE">site/language/de-DE/de-DE.com_bar.ini</language>
	</languages>

Expected result

Site showing whatever content is provided through the tmpl/default.php

Actual result

Site shows error: 404 View not found [name, type, prefix]: foo, html, foo\component\bar\site\controller\displayView

System information (as much as possible)

I am running Joomla! 4.1.5 locally through XAMPP on my Windows 10 Machine.

Windows: 10.0 build 19043 (Windows 10) AMD64
PHP Version: 7.4.29
Joomla Version: 4.1.5 (fresh installation)
Database Version: 10.4.24-MariaDB
Web Server: Apache/2.4.53 (Win64) OpenSSL/1.1.1n PHP/7.4.29

Additional comments

I was following along this blog post. The back-end part of the component, consisting of multiple View classes and one DisplayController works perfectly fine, but not the front-end part.

After a bit of debugging of the Joomla! Controller code it seems like the view isn't fetched properly even tho its name is fetched properly. I couldn't figure out why tho.

The following error is shown in the php debug bar:

error - Uncaught Throwable of type Exception thrown with message "View not found [Name, Type, Prefix]: foo, html, foo\component\bar\site\controller\displayView".

Stack trace:
#0 [ROOT]\libraries\src\MVC\Controller\BaseController.php(646): Joomla\CMS\MVC\Controller\BaseController->getView('foo', 'html', 'foo\\component\\b...', Array)
#1 [ROOT]\components\com_bar\src\Controller\DisplayController.php(34): Joomla\CMS\MVC\Controller\BaseController->display(false, Array)
#2 [ROOT]\libraries\src\MVC\Controller\BaseController.php(735): Foo\Component\Bar\Site\Controller\DisplayController->display()
#3 [ROOT]\libraries\src\Dispatcher\ComponentDispatcher.php(146): Joomla\CMS\MVC\Controller\BaseController->execute('display')
#4 [ROOT]\libraries\src\Component\ComponentHelper.php(389): Joomla\CMS\Dispatcher\ComponentDispatcher->dispatch()
#5 [ROOT]\libraries\src\Application\SiteApplication.php(204): Joomla\CMS\Component\ComponentHelper::renderComponent('com_bar')
#6 [ROOT]\libraries\src\Application\SiteApplication.php(243): Joomla\CMS\Application\SiteApplication->dispatch()
#7 [ROOT]\libraries\src\Application\CMSApplication.php(278): Joomla\CMS\Application\SiteApplication->doExecute()
#8 [ROOT]\includes\app.php(63): Joomla\CMS\Application\CMSApplication->execute()
#9 [ROOT]\index.php(32): require_once('C:\\Apps\\xampp\\h...')
#10 {main}