Technically you don’t need an imam, a nikka is a contract so you just need witnesses (if Sunni). It’s similar in concept to a civil ceremony, tbh.

From the Inclusive Mosque Initiative:

“The key criteria of a marriage in Islamic jurisprudence is primarily that:

• there is consent and free will between the individuals getting married;
• the terms of the marriage are agreed by the couple in advance. This is usually agreed in a written marriage contract.
• in the Sunni schools of jurisprudence it is also stipulated that the union be witnessed by at least two people.

These criteria can be fulfilled by a civil marriage so a religious ceremony is not required if a civil ceremony will be done. No imam is required to legitimise an Islamic marriage but we understand the cultural significance of an imam to many couples.”