How to fix a currently frozen iPhone XR?

iPhone XR is currently frozen. Can unlock the Lock Screen with passcode but no apps will open. Have tried turning off phone but it only activates Siri, who says she cannot power down the phone. When unlocked I’m able to swipe up and close all previously open apps but the single app/screen remains open, the purple smoke wave-like default screen. Phone calls come through the phone but I cannot answer them on the screen - have to answer on the connected iwatch. Do not want to hard reset and lose things that are not backed up. Any recommendations to try?

[Re-Titled by Moderator]