Yes, minors can apply for IPOs through Zerodha using UPI.
If UPI is not enabled for minor accounts, you can use the net banking ASBA route and provide the minor's demat account information to apply (subject to your bank's policies on minors applying for IPOs). If the minor uses someone else's bank or demat account, the RTA may decline the application.
You can enable Kite access for minors if it's not already enabled.