I had read some time ago that the Principality of Seborga was planning to join the Unrepresented Nations and Peoples Organization (UNPO).
Apparently their application was more than just politely acknowledged, and then in fact ignored, as my appeal was years ago, and for the micronation of TTF-Bucksfan.
The Principality of Seborga seemed like they really had “the foot in the door”, and it was only a question of time, and they would join not the diplomatic equivalent of the Italian Serie A (the United Nations), but at least the diplomatic equivalent of the Italian Serie B (the UNPO).
It did not happen. You can check for yourself also, but Seborga, or the Principality of Seborga, is still not listed at the UNPO members page.
However, even though I’m not involved with this, I do believe that I understand what actually happened, and the UNPO, or some people involved with the UNPO, eventually started an organisation that small nations like the Principality of Seborga could participate in. The n-result seems to be the Union of Small Nations:
It is certainly not for every small nation, as one needs to agree completely with the Charter of the Union of Small Nations, one needs to have excess diplomats, needs to be well-organised, and also needs to pay an annual membership fee of Euros 250.00 (circa USD 333.08). However, it definitely has potential for at least a wonderful ego trip, and perhaps with some real diplomatic gains, at least in the long term.
The Principality of Seborga is listed under the Project Nations list, along with the Principality of New Utopia, the Government of Antarcticland, and the Principality of Sealand, and the Principality of Hutt River is actually listed under the Small Nations section. There is also a section for Governments in Exile, with members like the Kingdom of Tibet, the Union of Burma, the Kingdom of Ethiopia, and the Republic of Somaliland.
As I said, membership is clearly not for every nation or micronation, and membership may, or may not have, long-term privileges.