Thunderbird
Different way of workingFreeNot a replacement for the account, just a different window onto it. Works with Proton through Bridge, which needs a paid plan.
Your files: Reads the same Proton mailbox through Bridge. Nothing to convert.
Does Proton Mail run on Linux?
Verdict: Yes
Yes. Proton ships a Linux desktop app, listed on its own download page as a beta, and the web version works in any Linux browser, so your mail comes with you.
Proton lists macOS, Windows and Linux on the Proton Mail desktop download page. The Linux app is marked beta, which is Proton's own word for it, so treat it as usable but still being finished. For Ubuntu it is also on the Snap Store, which is an app store already built into Ubuntu.
The web version is the fallback and it is not a poor one, because Proton Mail was a website first. Sign in at the same address in Firefox or Chrome and everything is there. Nothing on your Windows machine needs exporting, since your mail lives in Proton's servers in encrypted form.
If you used Proton Mail Bridge to read Proton mail inside Outlook or Thunderbird, Bridge has a Linux version too, and it needs a paid Proton plan just as it did on Windows. That route lets you keep using Thunderbird on Linux with your Proton account.
One habit to carry across. Proton encryption means Proton cannot reset your password for you in the way a normal provider can, so make sure your recovery phrase or recovery file is written down and stored somewhere other than the computer you are about to wipe.
Proton Mail on Linux, and alternatives
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