Olvid is a messaging service from France which is useable without a phone number and accessible under Android and iOS (which allows running it on a tablet without a SIM-Card). It provides an end-to-end encryption which includes metadata and thereby can assure anonymity of its users.
European instant messaging apps
An instant messaging app allows people to send text messages and also media to each other. Many of them also support voice calls and video calls. There is a separate category for team communication services, which offer similar functions, but focuses on communication in a team, therefore also offers many additional features that would not be useful for private communication, like for instance integrations in project management software.
This category contains services from companies based in a member state of the European Union (EU), the European Economic Area (EEA) and the European Free Trade Association (EFTA).
You can read more about the listing criteria the listing criteria.
European services
Threema Private is an instant messaging app for individuals from Switzerland, available for iOS, Android, Windows, macOS and Linux, and downloadable from the App Store and Google Play. Messages are end-to-end encrypted, and the mobile and desktop client apps are published under the AGPL-3.0 open-source license, while the server software that relays and stores messages remains proprietary. Because encryption and decryption take place only on users' own devices, the server cannot read message content, which limits how much the proprietary server code affects the confidentiality of communication. Threema Private is the individual-user product from Threema AG, distinct from Threema Work, the company's separate offering for businesses and organizations.
ginlo Private is a instant messaging app from ginlo. ginlo is a company from Germany that also offers ginlo Business, a team communication service.
The app can be downloaded here:
SKRED is an end-to-end encrypted and peer-to-peer instant messaging service from France. They don't require a phone number or email address for usage and store minimal information (account token) about their users. Due to their peer-to-peer implementation, they can't store metadata about messages and don't restrict what files or messages you can send.