Altering language code?

Hello, and thank you for this useful module!

On my site, our language codes include the country code as well, for instance /en-ca and /en-gb. So, I'd like to strip the country code off before passing it to Cookiebot via the data-culture attribute.

I noticed there was a cookiebot-gtm-declaration.html.twig, so I tried creating a theme_preprocess_cookiebot_gtm_declaration(&$variables) in my .theme file (to alter the #language variable) but the function is not being called.

Do you have a suggestion for me?

Thanks!