That strange phenomenon of a UN (United Nations) logo / flag / emblem mysteriously appearing in the top bar / panel of Ubuntu MATE was discussed a few months ago (June 2024), here in the "Ubuntu MATE Community", in the following discussion topic (started by @surfrock66):
If you read that topic, you can find the following answer by @ironfoot (accepted as being the "Solution" of that topic) where @ironfoot found the likely "cause" of the issue ("un" = "United Nations" but also "un" = "update notifier" !):
