TYPO3 HTML5 closing tags

I have set the following in the typoscript:

config.doctype = html5

nevertheless I get the following output:

<meta http-equiv="x-ua-compatible" content="IE=edge" />
<meta name="generator" content="TYPO3 CMS" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta name="robots" content="index, follow" />
<meta name="author" content="test" />
<meta name="keywords" content="TYPO3" />
<meta name="description" content="Bootstrap" />
<meta name="twitter:card" content="summary" />

I want to remove the slashes at the end. How can I do that?

I also get the slash on some content items

<img class="image-embed-item" title="title" alt="alt" width="50" height="50" loading="lazy" />

that should also be removed. What is the best way to proceed?

I also think, that this is waste of time. But if you really need to do this you could add the meta-data via TypoScript headerdata:

page.headerData {
10 = TEXT
10.value (
    <meta http-equiv="x-ua-compatible" content="IE=edge">
    <meta name="generator" content="TYPO3 CMS">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="robots" content="index, follow">
    <meta name="author" content="test">
    <meta name="keywords" content="TYPO3">
    <meta name="description" content="Bootstrap">
    <meta name="twitter:card" content="summary">
)

}

Check in the TypoScript-Object-Browser if 10 is occupied before. In case it is use a free number. (i.e. 20

To remove the slash in the image tag, i think the only way is to implement your own viewhelper. Maybe you could xclass the tag-based-viewhelper to achive non-closing tags for all tag-based viewhelper.

EDIT:

If all that doesn't fit your requirements, the only way i see is to implement a middleware to remove all the closing tags.

First implement the configuration in your extension.

/Configuration/RequestMiddlewares.php

<?php

return [
    'frontend' => [
        'remove-closing-tags-middleware' => [
            'target' => \VENDOR\ExtName\Middleware\RemoveClosingTagsMiddleware::class,
            'after' => [
                // Check Configuration for middlewares in Backend and replace last-middleware
                // as described here: https://docs.typo3.org/m/typo3/reference-coreapi/10.4/en-us/ApiOverview/RequestHandling/Index.html#debugging
                'last-middleware',
            ]
        ],
    ]
];

And then implement the middleware in your extension.

/Classes/Middleware/RemoveClosingTagsMiddleware.php

<?php
namespace VENDOR\ExtName\Middleware;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Server\MiddlewareInterface;
use Psr\Http\Server\RequestHandlerInterface;
use TYPO3\CMS\Core\Http\NullResponse;
use TYPO3\CMS\Core\Http\Stream;

class RemoveClosingTagsMiddleware implements MiddlewareInterface
{


    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
    {
        $response = $handler->handle($request);
        if ($response instanceof NullResponse) {
            return $response;
        }
        $body = $response->getBody();
        $body->rewind();
        $content = $response->getBody()->getContents();
        $content = str_replace('/>', '>', $content);
        $body = new Stream('php://temp', 'rw');
        $body->write($content);
        return $response->withBody($body);
    }
}

Don't forget to adjust VENDOR and ExtName to your extension.

Further information can be found here:

https://docs.typo3.org/m/typo3/reference-coreapi/10.4/en-us/ApiOverview/RequestHandling/Index.html

and here:

https://reelworx.at/blog/detail/correct-manipulation-of-generated-html-in-typo3/