We've been running Invision Community v5 without an issue on PHP 8.4 for about a year now. I know it is not supported. However with this new 'supported' version checks we ran in to issue not being able to upgrade. We bypassed it by switching temporary to PHP 8.3. However the tasks are also failing if you use cron. If you comment out in applications/core/interface/task/task.php supported check it will work again. Hopefully we get support soon for newer PHP versions as they improve performance a bit for websites.