I made a prototype of Kirigami-based client: https://git.sr.ht/~link2xt/kdeltachat
It is not ready for day-to-day use, but testing on Pinephone and patches that make it work for you are very welcome. I have not set up an issue tracker or mailing list, but you can PM me here, ping me on freenode deltachat channel or send patches directly to the email listed in commit messages.