Troubleshoot ublue-os/bluefin#575 directly

[ethanjli]

This PR is made to use GitHub Actions to build OS images so that I can try to bisect changes made by the standard Bluefin Containerfile to troubleshoot ublue-os#575 directly.

[ethanjli]

In the above commit, the Discord Flatpak app becomes able to open links.

[ethanjli]

Note: the above commit actually should be called "Restore Requires= for apps which didn't cause trouble with Requires= in #3". In that commit, the Discord Flatpak app becomes unable to open links. Interesting! The apps whose "Requires=" were enabled by the commit didn't cause any problems in #3 when their "Requires=" were allowed there.

[ethanjli]

In the above comit, the Discord Flatpak app becomes able to open links again.

[ethanjli]

In the above commit, the Discord Flatpak app is still able to open links. This means that it's either Syncthingy or bluefin-firstboot which appears to break xdg-desktop-portal when it's included in a Required= directive by ublue-user-setup.service. If bluefin-firstboot turns out to be the source of the problem here, we might be explain the different result from #3 with the fact that yafti can't even start running in #3 because it can't find Adwaita there.

[ethanjli]

In the above commit, the Discord Flatpak is no longer able to open links, and SyncThingy does a coredump at startup. This suggests the Syncthingy seems to break xdg-desktop-portal when it's included in a Required= directive by ublue-user-setup.service. I have no explanation for why SyncThingy would break link-opening here but not in #3.

[ethanjli]

In the above commit, the Discord Flatpak is able to open links again. and SyncThingy successfully launches as a background app. This confirms that including Requires=app-com.github.zocker_160.SyncThingy@autostart.service in ublue-user-setup.service is necessary to break xdg-desktop-portal stuff.

[ethanjli]

In the above commit, the Discord Flatpak is no longer able to open links, and SyncThingy crashes and coredumps at startup, and it no longer appears as a background app in the GNOME control center thing. This confirms that including Requires=app-com.github.zocker_160.SyncThingy@autostart.service in ublue-user-setup.service is necessary and sufficient to break xdg-desktop-portal stuff.

After I delete SyncThingy from the GNOME's Flatpack app store thing and restart, the Discord Flatpak is able to open links!

[ethanjli]

This issue should be resolved by #6