All test builds for Glimpse are hosted on https://build.glimpse-editor.org
If you haven't done so already, you first need to install Flatpak and enable Flathub on your machine. Glimpse depends on the GNOME platform runtime which is distributed by Flathub.
We provide our own Flatpak repository with builds from our development branch. To enable it, just run the following command in a terminal:
$ flatpak remote-add --if-not-exists --user glimpse_devel https://build.glimpse-editor.org/dev/flatpak/glimpse-devel.flatpakrepo
Next, either find Glimpse development builds in your software center, or install it in a terminal:
$ flatpak install glimpse_devel org.glimpse_editor.Glimpse