what is the opinion of rabbanim to come to Uman on RH ?
ב"ה Shalom, In order to answer your question, I will divide my answer in to 3 parts.1. Going to Uman, 2. praying on the burial place of Tzaddikim, and 3. worship of Hashem in general. Obviously, for Breslav Chassidim, going to Uman for Rosh Hashana epitomizes the connection with the Rebbe and it is the ultimate Tefilla of the year. It is mentioned extensively in the writings of Rav Nachman zt"l. According to our Rabbis in the Talmud, it is certainly virtuous to pray at the burial place of Tzaddikim for the Tzaddikim then pray for those who visit them, as evident from the well known Gemara in Sotah 34b, (and many other sources) that Caleb went to Chevron to pray at the Me'arat Hamachpela at the gravesites of our forefathers, so that G-d save him from the scheme of the spies. The Mishna Berura ( 581:27) says that at the resting place of Tzaddikim, prayers are more accepted. However, people should not direct their prayers to the Tzaddikim but to Hashem asking mercy for themselves in merit of the Tzaddikim. However, according to some Rabbis, although virtuous, we can't actually call praying at the burial place of Tzaddikim an actual Mitzvah. (See Rav Kook zt'l משפט כהן סי' קמז,in , and Rav Yitzchak Hacohen Rappaport zt"l (1679-1755) in בתי כהונה ח"א סי' כ"ג.) Even those, who do see it as a mitzvah, Rav Chizkiyya Medini zt"l (1832-1904) in מערכת ארץ ישראל סי' א, and Rav Avraham Meyuchas zt"l (1718-1768) in שדה הארץ אבן העזר סי' י"א , don't justify prolonged periods of abstaining from Torah learning due to this. Rav Meyuchas adds that if there is to any danger in travelling to the burial place of Tzaddikim it must be avoided. There are yet other aspects to be discussed, which I will not get into now, one of which is if one may leave Eretz Yisrael to pray at the at the resting place of Tzaddikim. There is yet another aspect to be dealt with and that is one's personal worship of Hashem. This refers to your wording "what is the opinion of Rabbanim?" No one questions Rav Nachman being a great Tzaddik. As you know for sure, there are different opinions among Rabbanim. Everyone follows their Rabbi. Every Jew has to live within framework of Jewish law. In addition to this, people have family and/ or community customs which they follow. There are many beautiful customs within the Jewish communities which due to the diaspora were spread all of the world. However, in order to reach our Jewish fulfillment we don't have to keep every Jewish custom from all the different communities. We fulfill that which we are required and that which brings us closer to our serving of Hashem. All the best