Yes and No:
Yes: In theory, if you add a brand new adhesive gasket to the frame on the inside, it should IN THEORY reseal the phone. You will need to remove the old adhesive gasket and make sure no residue is left by using isopropyl alcohol then apply the new gasket and I would say reheat the back pannel at around 110 C for maybe 1 min with a heat gun or heat plate then put the back on the phone this is to make it sticky and seal properly and put a few heavy books on it for a few hours but 24 hours is recommended this should recreate the seal.
No: Even from the start the manufacture does not guarantee any insurance from water damage and this is because your phone is never truly waterproof and the gasket seal will wear and tear over time after all it is a rubber type of double-sided sticky tape layer that keeps the back on the phone and prevents water from getting in.
But how important is the repair I need to change my LG v30+ battery as it doesn’t hold a charge anymore and needs a power bank 24/7, would you rather have a non-functional waterproof / water resistant phone or a fully functional non-waterproof / water-resistant phone. I know what id rather have and if the screen is cracked your phone’s water resistance is compromised anyway.
Adhesive Gasket Tape: https://www.ebay.co.uk/itm/184392178454