Trial access keys can (but are not required to) be issued by various project representatives. Basically, they are issued by emissaries (at the moment the issue is suspended), you can contact them. They can be found on the project forum and in the official community of the project in various social networks.
You can also get keys by participating in various activities: sweepstakes, contests, various offline events. You can learn more about this in the conditions of the activities.
IMPORTANT: If you are offered to purchase a temporary key - do not do this, temporary keys are issued for FREE!