Turn off all things under Siri (Before Searching, Content from Apple, Suggestions from Apple). Also check your Analytics and Privacy Reports (they tend to "reset" and turn them back on after a major update I noticed), turn off all Background App Refreshes (just leave it "On" on the top, but uncheck everything, it will still come in just fine); Remove notifications for Apple things that you don't use (like Screen Time, App Store, I turn them off); Under Location Services, check that all of them are "While Using" or "Never", and not "All the time", and try not to use Precise Location; Under System Services, turn off "Product Improvement". Under "Privacy and Security", turn off "Research Sensor & Sensor Data" if you don't use. Under "App Store", don't use Automatic Downloads. Turn off "Exposure Notifications" under Settings. Turn off "Tracking" under "Privacy and Security" too.
These are some of the things I did and battery life holds out pretty good.