Wifi frequently is disconnecting from the source where other phones are perfectly working

Connect to the WiFi network in question.

1. Launch the Settings app.
2. Tap Wi-Fi.
3. Tap the Info button next to the WiFi network name. (It looks like a lower-case 'i' in a circle.)
4. Ensure that the Auto-Join switch is on.
5. If Auto-Join is off, turn it on

Have you tried forgetting the network and reconnecting for reassigning your IP address from DHCP pool. At times when you move from one network to another the wifi at times does not immediately get hooked on to home wifi. 

Consider more secure wifi configuration.

Change your router’s WiFi to use WPA2-AES (CCMP) with no WPA or TKIP. Updating this setting ensures that your devices always connect in one encryption mode

1. TKIP is obsolete and not considered secure. Choose WPA2, the latest encryption standard, with AES encryption for optimal security
2. If your router doesn’t specify TKIP or AES, the WPA2 option probably uses AES

Try a Reset ALL Settings.

This is usually the last resort since it resets all your personalised features back to factory defaults

Go to Settings > General > Reset > Reset All Settings

• • This resets to default everything in Settings, including notifications, alerts, brightness, and clock settings like wake up alarms
  • Resetting all settings also reverts all your personalised and customised features like wallpapers and accessibility settings back to factory defaults.
  • Performing this action does not impact any of your personal device data, including photos, texts, documents, and other files
  • You need to reconfigure these settings once your iPhone or iDevice restarts

Privacy Settings

1. Toggle off Location Services. Go to Settings > Privacy > Location Services and turn it off
2. Many users find that disabling System Services’ WiFi Networking solves the problem
3. Go to Settings > Privacy > Location Services > System Services > and toggle off WiFi Networking

Restart your iDevice. If a normal restart does not help, perform a forced restart by holding down these buttons at the same time for at least ten seconds until the Apple logo appears

1. On an iPhone 6S or below plus all iPads & iPod Touches, press Home and Power at the same time until you see the Apple logo
2. For iPhone 7 or iPhone 7 Plus: Press and hold both the Side and Volume Down buttons for at least 10 seconds, until you see the Apple logo
3. On an iPhone X Series model (XS/XR/X) or iPhone 8 or iPhone 8 Plus: Press and quickly release the Volume Up button. Then press and quickly release the Volume Down button. Finally, press and hold the Side button until you see the Apple Logo

Connect to Wi-Fi on your iPhone, iPad, or iPod touch - Apple Support

https://support.apple.com/en-in/HT202639

I've been encountering this issue ever since I got the XR myself back in November. For me I am using the phone as normal on the same connection I've used my previous iPhone 7 on with no issue & suddenly (with the wifi symbol still showing full connection) I would notice that I am getting no connection. After a couple of seconds in some cases the symbol would disappear completely & would either come back on its own or I would have to go to Settings > Wifi & reconnect there or Control Centre & toggle the connection there. Been extremely frustrating to deal with. Also I've noticed that the XR's ability to use 5GHz connections is not as good as (in my case) the iPhone 7 which I regularly used the 5GHz connection with 0 drop off vs the XR which struggles to connect & when it does connect almost immediately drops off.

I am hoping, against slowly losing odds, that this is software related but I am thinking it is hardware & common enough an issue as well from what I've read.