Blank screen when selecting COSMIC at login

[braydonf]

After compiling and enabling the cosmic-sysext (via https://github.com/pop-os/cosmic-epoch#testing) the "COSMIC" option was correctly displayed alongside "GNOME" and "Ubuntu" at the login screen; however, after logging in with the user, the screen went completely blank.

• OS: Ubuntu 26.04
• Hardware: RISC-V / Spacemit K3 Pico-ITX (Milk V Jupiter 2)
• Cosmic Epoch: 1.3.0

A few modifications were necessary to complete the build:

1. Several rust-toolchain.toml and Cargo.toml files in submodules were updated to use Rust 1.97.1. This was to resolve build issues due to several sigsegv errors.
2. The justfile was updated to use just instead of make for xdg-desktop-portal-cosmic as in Fix just sysext build #3670

[Drakulix]

Hmm, I cannot really help you with this without any logs, since I would guess this is related to your rather special hardware. I am not sure anyone every tried running cosmic on RISC-V.

It might be that rustix is having problems with syscalls on your platform or 3d acceleration not being available or ... (all speculative)

[braydonf]

What is the method to get logs for this?

[Drakulix]

They should be in your users journald log. So simply running something like journalctl --user -g cosmic should give you the relevant bits.

[braydonf]

Okay, after refreshing cosmic-sysext and rebooting, I was able to select COSMIC and not get a blank screen! Instead, a few basic user interface elements appeared: a grey background, a mouse, a context menu on right-click, and access to search / app launcher at the top of the screen when using the super key. I tried to open cosmic-settings to change the display settings via the right-click menu; however, it crashed with a sigabrt. I wasn't able to launch any other applications yet. I was able to select shut down from the search menu.

Here are the logs from that session:

• https://github.com/user-attachments/files/30129143/cosmic-logs.txt
• https://gist.github.com/braydonf/5b41e497bccf116534121170489c929a

[Drakulix]

I don't see anything in particular in these logs, that would be specific to RISC-V, but rather:

• Lots of missing config files
• Some expected services missing like the dbus UPower interface

At this point I recommend going for proper packaging of the components. I don't think Ubuntu has official cosmic packages, but you might have success with this ppa (https://launchpad.net/~hepp3n/+archive/ubuntu/cosmic-epoch), though you would probably need to download the src.deb packages and build them for your architecture yourself.

The sysext is mostly meant for developing and not as a full blown install on arbitrary distributions (we cannot provide that).

[braydonf]

A few progress updates:

• With this hardware and OS, compiling with Rust 1.93.1 has worked with the exception of cosmic-monitor that required Rust 1.95 for the sysinfo package. It's unclear why I had previous issues; perhaps a bug was fixed in the minor version or I was running another Rust version with rustup.
• Using Ubuntu 26.04 packaged Rust toolchain has worked (1.93.1)
• Installing into /usr/local or /usr via sudo just install resulted in the same result as previous builds with using sysext. There may have been files left from a previous install, as the install to /usr was after a manual attempt to clean the installed files.
• Building Debian packages requires adding riscv64 to the Architecture field in the various ./debian/control files to support the binary build with dpkg-buildpackage and apt-src (e.g., from the source files at the PPA: https://launchpad.net/~hepp3n/+archive/ubuntu/cosmic-epoch)

[braydonf]

Okay, I was able to use apt-src to build all the packages from https://launchpad.net/~hepp3n/+archive/ubuntu/cosmic-epoch:

• Skipped cosmic-monitor due to a Rust version dependency requirement that was not available from Ubuntu 26.04 sources.
• Adding riscv64 to ./debian/control as an architecture was necessary across several packages.
• Building xdg-desktop-portal-cosmic required setting SOURCE_GIT_HASH and SOURCE_DATE_EPOCH environment variables.

After rebooting the cosmic-greeter displayed the login options; however, after attempting to login it went to a blank screen. Here are the logs from the session:

• https://github.com/user-attachments/files/30245258/cosmic-logs-2.txt
• https://gist.github.com/braydonf/a318bffa2aada0e44759568064f8ebe7

[braydonf]

A few more logs from running individual programs:

ubuntu@ubuntu:~$ cosmic-app-library 
 ERROR i18n_embed::requester > Unable to parse your locale: ParserError(InvalidLanguage)
 ERROR cosmic::theme         > error loading system dark theme error=GetKey("list_button", Os { code: 2, kind: NotFound, message: "No such file or directory" })
 
ubuntu@ubuntu:~$ cosmic-edit 
[2026-07-22T00:27:38Z ERROR i18n_embed::requester] Unable to parse your locale: ParserError(InvalidLanguage)
[2026-07-22T00:27:38Z ERROR cosmic::theme] error loading system dark theme error=GetKey("list_button", Os { code: 2, kind: NotFound, message: "No such file or directory" })

ubuntu@ubuntu:~$ cosmic-files
  2026-07-22T00:31:05.287699Z ERROR  Unable to parse your locale: ParserError(InvalidLanguage)
    at /home/ubuntu/software/cosmic-epoch-packages/cosmic-files-1.3.0~5278c67/vendor/i18n-embed/src/requester.rs:293 on main

  2026-07-22T00:31:05.300639Z ERROR  error loading system dark theme, error: GetKey("list_button", Os { code: 2, kind: NotFound, message: "No such file or directory" })
    at /home/ubuntu/software/cosmic-epoch-packages/cosmic-files-1.3.0~5278c67/vendor/libcosmic/src/theme/mod.rs:95 on main

Full logs:

• https://github.com/user-attachments/files/30248003/other-logs.txt
• https://gist.github.com/braydonf/db2b405c65653798cc2c36262136a92b

[braydonf]

Tried again with a fresh install of Ubuntu. The only package that didn't install was cosmic-desktop-minimal due to uninstallable dependencies, namely firefox, fwupd-signed, hwctl, and memtest86+. It would be possible to build firefox to fix that; it's unclear about the others.

This time it was possible to select COSMIC from gdm3; however, other applications didn't launch, such a cosmic-settings. It was possible to start chromium. Attempting to run cosmic-files from GNOME, as in the previous comment, resulted in the same error logs.