I finally just rage-built the Kanban board I've wanted for years, mostly for retros and other structured discussions:

https://www.kanbanish.com

Features that I wanted, which I couldn't find all together in any other apps:

- No signups at all

- Anyone can edit anything on the board

- Comments, voting, emoji reactions

- The ability to vote multiple times on the same card (useful for Lean Coffee)

- A bunch of templates for common retro/discussion formats

- Export the board contents to plain text or markdown for meeting notes