Which countries keep GMT?

Could you elaborate on which countries observe Greenwich Mean Time (GMT) as their standard time zone? GMT, which is also referred to as Universal Time Coordinated (UTC), serves as the primary time standard by which the world regulates clocks and time. While it's technically not a time zone in the traditional sense, it is often used as a reference for other time zones. Several countries and territories around the world set their clocks to UTC or UTC+0, which is equivalent to GMT. Some notable examples include the United Kingdom, Portugal, Iceland, and the Canary Islands. However, there are also numerous territories and island nations that utilize UTC+0 or a variation of it for their standard time. Could you provide me with a more specific list of countries that adhere to GMT or UTC+0?