The Proton Mail desktop apps for Windows and macOS are now accessible in beta to all supporters on paid subscriptions
From the team:
Hi everyone,
As a result of your valuable feedback, we've been working on making Proton Mail and Calendar easier to use on your desktop.
Today, we reached a significant milestone - the Proton Mail and Calendar desktop apps for Windows and macOS are now available in beta for all supporters on paid Proton plans. We're also working on the Linux app and will release it soon for testing.
But Proton also insists on doing the packaging and distribution of it outside the ordinary distribution paths Linux distros uses (apt/yum/dnf repos or flatpak) ... So they waste time and energy on getting stuff working properly across a broader range of Linux distributions.
The end result will therefore most likely be a poorer user experience where some features don't work well on some distros. Depending on how their "package" will manage to integrate on the distro installing it.