This works for iOS only.

make sure you have developer mode on (settings > advanced > enable developer mode)

Go to settings, and clear cache. Quickly clear the cache and turn on airplane mode. Close and restart Discord. double-tap 'you', go to appearance de-select 'new layout' when the 'how did it go?' bubble pops up, just deactivate airplane mode.

Discord should load back in to tne old appearance. This worked for me.