Hello there,
my customer insists on having the mobile menu customized to be on the right instead of the left side. I know it would be possible by changing the class to .uk-navbar-flip but I absolutely can't find where to change the class. Is it possible somehow?

Thank you in advance!

Hi there,
you can add the uk-offcanvas-bar-flip to the layouts/theme.php > Line 161

<div id="offcanvas" class="uk-offcanvas">
<div class="uk-offcanvas-bar uk-offcanvas-bar-flip"><?php echo $this->render('offcanvas'); ?></div>
</div>

But please do not edit the org file. Always create an override and customize the new files in:
styles/your new style/layouts/theme.php

To customize the general theme layout, you need to override the /layouts/theme.php. To do so, create the /styles/STYLE-NAME/layouts directory, copy the file in there and start adding your own PHP code.

Awesome, Problem solved!