Email address used to download the app to the device can be found here:
RCTAsyncLocalStorage_V1/manifest.json
The userid and email can be found here in an iOS device: /private/var/mobile/Containers/Data/Application/*UUID*/Documents/mmkv/mmkv.default
Search for user_id_cache and email_cache.
In Windows they can be found here:
USER/appdata/roaming/discord/Local Storage/leveldb/000003.log
Search for user_id_cache and email_cache It's only the user id, and not the username. Search the messages in the cache.db (iOS) or 50.json (Windows) to match up the userid with the username.
Thank you so much TheKateCain. Super useful information!