@Harshit Kumar Upadhyay If UPI (platform like phone pe, gpay, bhim - does not matter) is linked to bank where PAN is same as in demat account, it is not third party. But UPI is linked to bank where PAN belongs to some other person, it certainly is third party and has been BANNED. So your question is like asking, guide me how not to get penalised while driving without a helmet.
Consider this suggestion if you are interested. Make use of ASBA feature of ICICI bank (or any other bank) for applying in IPO. In case of ICICI bank, open the portal, go to link Invest in IPO, choose IPO, fill relevant details (like DP ID) and it's done !