Limit the available phone number country code in pretix phone number questions. Caution! Applies to the whole server! This plugin does not even have to be activated. As soon as you install it, it overrides the phone number prefixes available server-wide.

It applies to both phone number questions and the pretix built-in phone number field. By default, this plugin restricts phone numbers to "+1 (USA)". If you want to place a different restriction, you can do so via the pretix configuration file.