https://meta.discourse.org/t/why-do-i-feel-writing-in-discourse-composer-became-slow/148948/4
Typing on a khadas vim3 is extremely slow. Bug has been patched.
Khadas please upgrade Discourse to beta. (mentioned in link)
Bugfix is here: https://github.com/discourse/discourse/commit/7132c50f3bb9776676c8a1ca6eff67227ef36d06