Implement Visual Viewport API support to improve on-screen keyboard experience
Interacting with the mobile UI while the on-screen keyboard is visible is rather painful and almost unusable at times, especially with iOS Safari when picking emojis.
The good news is that there is an API for fixing viewport issues now: https://developer.mozilla.org/en-US/docs/Web/API/Visual_Viewport_API
It's listed as a draft, but is supported by virtually all major browsers.
This is one of those things that could actually make the Pleroma mobile web UI work better than Mastodon's, because it's also bad when it comes to this.
What I'd personally like to see is for the picker to just go full screen above the keyboard. Let me pick my emoji and don't scroll partially out of view or do anything else until I've found and picked the emoji I want, or have closed the picker.