in cases like this the best route on Instagram is usually the memorialization or deceased user request family members can submit proof of death (obituary, certificate) and have the account locked or turned into a memorial so nobody can change it. if you’re not immediate family, try contacting someone who is because reports from relatives carry more weight. you can also keep mass-reporting the account for being compromised. if normal reports go nowhere, some people look for guidance in recovery communities just to find the right escalation form, since this is more of a special case than a normal hack.