Install on Linux with Flatpak

hypercal publishes its own Flatpak repository. Installing from it gives you updates through flatpak update, or through GNOME Software or KDE Discover, like any other Flatpak app.

Install

One command adds the repository and installs the app:

flatpak install --user https://hyper-calendar-7b58b2.gitlab.io/flatpak/dev.hypercalendar.Desktop.flatpakref

Drop --user to install for every account on the machine. Opening the same URL in a browser and handing the file to GNOME Software or Discover does the same thing.

The app runs on the Freedesktop 25.08 runtime, which comes from Flathub, not from this repository. The file above names Flathub as the runtime source, so if you do not have Flathub set up yet, Flatpak offers to add it.

Or add the repository first

If you would rather add the remote and install from it by name:

flatpak remote-add --user --if-not-exists hypercal https://hyper-calendar-7b58b2.gitlab.io/flatpak/hypercal.flatpakrepo
flatpak install --user hypercal dev.hypercalendar.Desktop

This route needs Flathub already added, for the runtime.

Updates

flatpak update

The repository always carries the newest stable release, and only that one. Release candidates are never published here.

Checking the signing key

The repository is signed with a GPG key, and both files above carry its public half. Flatpak pins that key when it adds the remote and rejects anything later that is signed by a different one. To check that the key you are about to pin is the right one:

curl -s https://hyper-calendar-7b58b2.gitlab.io/flatpak/hypercal.flatpakrepo \
  | sed -n 's/^GPGKey=//p' | base64 -d | gpg --show-keys

The fingerprint on the line under pub must be:

4851E4530D6C836FD971C3BF0CB66E5BE9D28FB2

It is also listed on Signing keys, which is served from the same site. The same key is committed in the repository's source, in scripts/build-flatpak-repo.sh.

This repository URL is permanent

It is derived from GitLab's "unique domain" Pages setting. If that is ever turned off the URL changes, and every installation has to remove the remote and add it again.

Coming from the downloaded bundle

If you installed a .flatpak file from a release page, that copy does not update. Move it onto the repository with:

flatpak remote-add --user --if-not-exists hypercal https://hyper-calendar-7b58b2.gitlab.io/flatpak/hypercal.flatpakrepo
flatpak install --user --reinstall hypercal dev.hypercalendar.Desktop

Your calendar stays. It lives in ~/.var/app/dev.hypercalendar.Desktop, and reinstalling does not touch that directory.

What you get

The same desktop app as the AppImage, deb, rpm and Arch packages: a calendar with its own database and its own backend, needing no account and no network. See The desktop app for what that means. That page also covers what the Flatpak sandbox allows and one known issue specific to it: the panel indicator does not appear.