A user reports that using his brand new Nokia 8110 4G running KaiOS - Wikipedia, Discourse reports the browser being too old an unsupported.
While its not officially supported, it should work fine provided the user is running KaiOS 3.0. What version is the user running?
From a quick search it appears that this is a 2018 phone, and KaiOS doesn’t ship software updates. That means its running Firefox 48 from 2016. That means the user will receive the basic HTML view that is read-only.
Are you sure that’s a “brand new” smartphone? As mentioned already, it was released in 2017.
Firefox OS, the operating system that KaiOS was forked from, was abandoned by Mozilla in 2016.