Is it Islamically permissible to pray in university halls with the intention of inviting non-Muslims and demonstrating the rituals of Islam? And does repeating this annually constitute an innovation (bid‘ah)?

Congregational prayer in the mosque is obligatory for whoever hears the call (adhan) with a normal voice. However, a legitimate need or a predominant benefit may permit praying in congregation outside the mosque. If it is highly probable that praying in a hall will affect non-Muslims and be a cause for some of them to embrace Islam, then there is no objection to praying there in congregation. Repeating this is not considered an innovation (bid'ah) if the intention is a legitimate benefit, such as inviting non-Muslims to Islam, provided that no specific day is designated for it. Rather, the matter depends on the need and choosing what is most suitable to gather the largest number of observers.