
AnonAddy
AnonAddy provides an email forwarding service that keeps personal email addresses private.

BigBlueButton
BigBlueButton is an open-source video communication tool with all the required features for online training and learning including breakout rooms, whiteboards, closed captioning, polls, shared notes, and more.
[S]ign up for BigBlueButton managed by NoLog.cz, CommunityBridge, meet.coop, and other providers.
– Digital Hygiene 101: How to practise digital safety and security

Briar
Briar is an open-source secure message app for Android. With Briar, users can send and receive messages through encrypted Bluetooth, WiFi, or Tor connections to avoid surveillance and censorship.

DuckDuckGo Email Protection
DuckDuckGo Email Protection is a service within DuckDuckGo browser extension that allows you to generate @duck.com forwarding email addresses to mask your personal email address. It automatically removes trackers in the forwarded emails to protect your privacy online.

Jitsi Meet
Jitsi Meet is an open-source private video conferencing software that limits the user’s digital footprint when meeting virtually. It works on most modern internet browsers and is also available as a mobile app for Android and iOS.
You can use meet.jit.si to host your online meetings for free […] Other trusted free Jitsi Meet deployments include Greenhost, Framatalk, and Distroot.
– Digital Hygiene 101: How to practise digital safety and security

K-9 Mail
K-9 Mail is an open source email client for Android with OpenPGP encryption support.

Mailvelope
Mailvelope is an open-source extension for Chromium- and Firefox-based web browsers that provides an interface for Pretty Good Protection (PGP) email encryption on popular web-based email services.

Mattermost
Mattermost is an open-source collaborative chat for teams.

Proton Mail
Proton Mail (Web, Android, iOS) is an open-source email service that uses end-to-end encryption and zero-access encryption to protect the user’s data and privacy.

Riseup Email
Riseup Email is a secure email service by activists for activists. Its security features include full-disk encryption, encrypted email storage, Onion routing, and more.

Session
Session is a decentralised instant messaging app that does not require phone numbers, email addresses, or other personally identifiable information.

Signal
Signal (Desktop, Android, iOS) is an open-source secure messaging and calling app that uses end-to-end encryption to protect the user’s privacy.

Skiff Mail
Skiff Mail is end-to-end encrypted email that protects your inbox and gives you the power to communicate freely.

Thunderbird
Thunderbird is an open-source desktop email client that has built-in security and safety features including remote image linking protection, phishing protection, PGP encryption, and more.

Tutanota
Tutanota provides secure, green, and ad-free email service that incorporates privacy by design.

Wire
Wire is a secure group communication suite that offers secure messaging, video conferencing, and file sharing.

Zulip
Zulip is an open-source collaborative chat for teams.