Homepage: An00nymushun/End-to-end-Discord-Encryption
For Chrome: SimpleDiscordCrypt
For Firefox: SimpleDiscordCrypt – Get this Extension for
Firefox (en-US) **Incompatibility**
Tampermonkey script: https://gitlab.com/An0/SimpleDiscordCrypt/raw/master/SimpleDiscordCrypt.user.js
For Chrome: SimpleDiscordCrypt
For Firefox: SimpleDiscordCrypt – Get this Extension for

Tampermonkey script: https://gitlab.com/An0/SimpleDiscordCrypt/raw/master/SimpleDiscordCrypt.user.js
Discord message encryption plugin, it gives end-to-end client side encryption for your messages and files with automatic key exchange, works without BetterDiscord
For Chrome (and similar) use the extension
If you have Discord installed, use the installer (Alt+click to download, right click on the downloaded file and Run with PowerShell)
For mobile you should try Yandex Browser, it's Chromium based and supports extensions
Firefox is kind of supported but there is incompatibility because of 1048931 - Add PKCS8 import/export for ECDH keys to WebCrypto API
If nothing works, install it as a userscript (with Tampermonkey) or include the js file somehow else
Please do not download this plugin from untrusted sources, for example there is one in chrome store with the same name