launch Siri on my iPhone XR

See the article https://support.apple.com/en-in/guide/iphone/iph83aad8922/ios

Set up Siri

If you didn’t set up Siri when you first set up your iPhone, go to Settings  > Siri & Search, then turn on the following:

• Listen for “Hey Siri”
• Press Side Button for Siri (on an iPhone with Face ID) or Press Home for Siri (on an iPhone with a Home button) .

Try and find an answer here --> If Siri or "Hey Siri" isn't working - Apple Support

To get Siri on Lock Screen --> Settings > Face ID and Passcode > Siri [Enable]