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Merkuro vs Thunderbird: catalog facts
Merkuro	Thunderbird
Free Free and open source under the GPL-3.0-or-later licence.	Free Free forever, funded by donations.
Linux	Windows, macOS, Linux, Android
Supports Nextcloud, Google Calendar, Outlook and CalDAV calendars Combines events, tasks and contacts in one app	Unified inbox across every account, or each account kept separate, your choice Mail, calendar, contacts and tasks in one application rather than four
Linux only Fits best within the KDE Plasma desktop	The interface carries a lot of history and can feel dense next to a webmail tab Major ESR releases have historically been disruptive for add-ons and settings
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0-or-later	License: MPL-2.0
Not stated if an account is needed	No account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked October 1, 2026	Official website Full listing and sources Checked September 20, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.