The Cat B35 is already out, thankfully! £99 direct from Cat, probably slightly more elsewhere.
It has a certain bulky charm to it, plus a scratch resistant screen, which is a big plus over the HMD 8110 4G. Given the pricepoint I'll probably end up getting one, to serve as a backup/featurephone w. hotspot and email. It covers most bases, and everything else is just residual habit from smartphone use (and the kind of thing that I don't mind not having if I, say, run out of juice on the android behemoth that lives in my trousers.
I do have some minor reservations about KaiOS, since I don't know how much information is able to be slurped from it via the inevitable google bloat. Possibly also worth considering that while whatsapp is available on the platform it's currently only available for Jio devices, and neither KaiOS/Whatsapp haven't made a statement of intent re:broader availability which might be an issue for some.