Does IPO allotment depend on broker?

No, IPO allotment is done by the registrar.

A broker is an intermediary that simply provides the trading platform for IPO application. In an IPO, the broker's role is to submit bids to the exchange.

The registrar is responsible for the entire allocation process. The Registrar finalizes the basis of allotment in consultation with the designated exchanges. Once the basis of allotment is determined, the Registrar instructs the banks to debit the bank accounts of the allottees and arrange for a refund in case of non-/partial allotment.