I’ve seen multiple iPhone XS, XS Max, and XR accross the Sprint network not be given an IPv4 address. As far as I was made aware of Sprint’s network is still configured for dual stack IP. I looked through and the problem seems to be within the carrier bundle Sprint is passing to these phones. They are passing the x.ispsn APN which I’ve been told is IPv6 only compared to 8 Plus using the n.ispsn APN which supports both. The issue stretches further than my devices. This issue is resulting not being able to access IPv4 only sites at all.
The pool of IPV4 addresses is being rapidly exhausted. Sprint is moving to IPV6 compliancy due to a government mandate. Sprint has recommended that enterprises convert to use IPv6 for several years. Have you possibly thought about using a different browser?
What is the site that your trying to access?