Element
Ownership: Privately held
Pricing: Free for self-hosted Matrix. Element Cloud from $5/user/month. Element Server Suite for on-premise enterprise.
Known for: Open-source team communication built on the Matrix protocol. End-to-end encrypted by default. Decentralised — talk across Matrix servers like email talks across domains. London-headquartered. The Matrix-protocol play. If you care about federation and not being locked into one vendor's network, this is structurally different from everything else here.
https://element.io
Fleep
Ownership: Privately held
Pricing: Free Basic plan with full message history (unlike Slack's free tier). Business €5/user/month. Estonia country page coming soon.
Known for: Estonian team chat with email interoperability — chat with anyone via email address, no signup required for the other side. Apps for iOS, Android, Windows, macOS, Linux. Pinboard for important items. The Slack alternative for cross-org chats. Email interop is unique and genuinely useful when you talk to clients outside your team.
https://fleep.io
ginlo Business
Ownership: Privately held
Pricing: €3.57/user/month. Free trial. Customised enterprise plans on request.
Known for: German enterprise messenger with end-to-end encryption. Audit-friendly, GDPR-compliant by default. Sister product ginlo Private for personal messaging. Cheap, focused, German. The right default for SMBs that need encrypted team chat without the Wire-level overkill.
https://www.ginlo.net/en/ginlo-business/
Infomaniak kChat
Ownership: Privately held
Pricing: Standard €1.58/user/month (first user free). Pro €3.29/user/month. Enterprise on request.
Known for: Swiss team chat from Infomaniak. Part of kSuite alongside kMail, kDrive, kCalendar. Renewable-energy hosted in Infomaniak's own Swiss data centres. The cheapest serious team chat in this list. Bundles with mail, drive, and calendar — one provider for your whole team stack.
https://www.infomaniak.com/en/kchat
Mattermost by Stackhero
Ownership: Privately held
Pricing: Managed instances from around €15-25/month for small teams. Larger plans for bigger orgs.
Known for: French-managed hosting of the open-source Mattermost server. Hosted on Scaleway and Hetzner, both renewable-energy data centres. Get the Mattermost experience without operating the infrastructure. Open-source Mattermost with European hosting and no ops burden. The best fit for tech teams that want Slack-like UX without the Slack data-residency problem.
https://www.stackhero.io/en-eu/services/Mattermost
Nextcloud Talk
Ownership: Privately held
Pricing: Free if you self-host. Enterprise support from €36/user/year (Nextcloud Hub pricing).
Known for: Open-source self-hostable team chat and video conferencing. End-to-end encrypted. Part of Nextcloud Hub alongside Files and Groupware. Used by EU institutions and Fortune 500 firms. If you control your own infrastructure, this is the answer. Self-hosted team chat without the Slack tax or the Microsoft tax.
https://nextcloud.com/talk/
Nozbe
Ownership: Privately held
Pricing: Free up to 3 users with 3 projects. Premium €8/user/month with unlimited projects and 20 GB storage.
Known for: Polish team chat that's actually a task and project tool with chat threads. Mobile-first design. Combines instant messaging, threads, and kanban boards in one app. Available on most platforms. Closer to Asana with messaging than Slack with tasks. The right pick if your team's pain is projects, not channels.
https://nozbe.com
Private Discuss
Ownership: Privately held
Pricing: Generous free plan. Paid plans from €12.50/month.
Known for: French team communication with a strong focus on audio and video conferences. Also offers instant messaging and apps for all major platforms. EU-hosted on OVHcloud. More Zoom-than-Slack, but the chat layer is solid. Best fit if your team's primary need is meetings with chat as the backchannel.
https://private-discuss.com
Stackfield
Ownership: Privately held
Pricing: No free plan. Plans from €45/month for 5 users (around €9/user/month).
Known for: German team communication platform with end-to-end encryption, chat, audio/video calls, task management, and file storage in one app. EU-hosted on the German Myra CDN. The most security-serious German Slack alternative. Built for regulated industries where E2E across every channel is mandatory.
https://www.stackfield.com
Wire
Ownership: Privately held
Pricing: Free up to 5 users. Enterprise $7.65/user/month.
Known for: Swiss team chat with end-to-end encryption by default across messages, calls, and file sharing. Open-source clients on every major platform. Used by governments and security-conscious enterprises. The most security-credible name in the list. If your threat model includes intelligence services, this is where serious orgs land.
https://wire.com