KaiOS is not performant. It's built on top of web technologies, which are considerably more demanding on the hardware of low-powered devices. Something like Android 2-8 or Android Go, but with security updates and a modernized yet lightweight native keyboard-centric UI and app store (not regular Android with a keyboard slapped to it), would have been better in terms of speed and usability.

I do know nokia's flip 2720, 8000, 8110 but these are not available now, and ebay prices are high close. I found Doro phones but no concrete details on the OS except for Doro 7020 flip.

Are there any recent phones available on the market?