Can you please provide some more information regarding these phones? I skimmed through Walmart's online store, but couldn't find any dumb 4G phones there. I'd be really interested to learn if they sell 4G capable feature phones not running KaiOS.
3G phones are unfortunately no better choice than 2G phones, because the 3G networks of most operators will be not running much longer than their 2G networks. Here in Europe operators often even plan to shut down their 3G networks prior to their 2G networks.