If you're sure that your iPhone XR does NOT connect to any Wifi Network and has no Internet access (I mean any public or private wifi network too), and since you're saying that you've already followed all the suggestions correctly provided by Joseph_S. (to no avail), I suspect that something could have gone wrong during the latest update.
I would try to install a fresh copy of iOS on your device, creating a full backup of your XR, then restoring it to factory settings and, in the end, setting it up as new. These are the instructions to perform that procedure:
Restore your iPhone, iPad, or iPod to factory settings – Apple Support
When done, test your iPhone for a while connecting it to 2 or more wifi networks, without restoring data from backup. If it doesn't work, have your device inspected at an Apple Store or AASP (they are reopening after the temporary lockdown), or contact Apple Support online using this link:--> Get Support
On the contrary, if it connects and has access to the Internet, you can exclude a hardware failure. Then restore data from your previously made backup. If the issue reappears, then your data or settings could be corrupt.
Please let us know how it goes.
Thanks and regards
Giulio