Mac is the main, Apple-checked product. Linux is optional and best-effort — fine if you already live in Linux; not required for a normal Mac purchase.
The .deb / AppImage desktop builds are invite-only right now (not a public download). After you buy, email [email protected] with your Stripe receipt — we’ll send a private download link and checksum.
These builds are not signed the way the Mac app is. Expect more DIY if something looks odd. SmartScreen-style warnings do not apply on Linux, but WebKitGTK must be installed for the windowed app.
If you only want the atto command (no windowed app):
SHA256 and pins: see README or ask Support.
After you buy, download your license from the claim page in your email and import it in Atto (or save as ~/.atto/license.json). Your family files stay in ~/AttoVault/ on disk; the app needs a valid license to open the vault.