Temporary upload button fix -

Hi Sarah,

I'm really glad you reached out—you're in the right place, and I'm happy to help you resolve this.

The issue where Add HTML before event content and Add HTML after event content fields under Events > Settings > Display > Additional Content tab strip out HTML tags is a bug that has been reported to our development team in the form of a bug report. 

Our development team is working on a fix for the issue which should be available in a plugin update. While I am unable to provide an ETA on the fix, I will link this ticket to the bug report so that you can be notified as soon as the fix is released.

Meanwhile, as a workaround, the following filter hooks can be used to add HTML before event content,
tribe_events_before_html
tribe_events_after_html

Here's an example demonstrating how the first filter hook can be used to add HTML before event content,

add_filter( 'tribe_events_before_html', function ( $content ) { 

$content .= '<div>'; 
$content .= '<h1>Heading One</h1> '; 
$content .= '<p>Lorem ipsum odor amet, <b>consectetuer</b> adipiscing elit.</p> '; 
$content .= '<a href="/events/"><button class="tribe-common-c-btn">Click Here</button></a>'; 
$content .= '</div>'; 

return $content; 
} );

Here's how you can add the PHP code snippet to your site,
https://theeventscalendar.com/knowledgebase/best-practices-for-implementing-custom-code-snippets/

Here's how the content added through the code snippet shared above will appear on the frontend,
https://i.imgur.com/V7ycT3h.png

Additionally, I'd recommend considering one of the alternative methods of showing your submission form as described in this article: Locating Links to Your Community Events Pages

Please let me know if you have any other questions.

Best regards,
Iris