Is the collective raising of voices in Takbir inside the mosque for an hour or so before the Eid prayers from the Sunnah and Islamically acceptable?

It is desirable to proclaim the takbir on the two nights of Eid, individually and in congregation. Its preferred wording is mentioned in Fatwa (definition) no. 39115. There is no harm in adding other dhikr such as tasbih, tahlil, and hawqalah, as stated by Al-Shafi'i. Therefore, there is no harm in performing dhikr in the mosques in your country, with the exception of the imam repeating the takbir or similar phrases along with the people, as there is no evidence to support its legitimacy, and consistently doing so might fall under the category of bid'ah idafiyyah (added innovation).