Bazzite / Fedora Atomic Megathread

[JankyMouse]

What is this?

This is a community megathread for installing and running Millennium (v3.6.3+ / 64-bit Steam client) on Bazzite and other Fedora Atomic / OSTree-based distributions.

Because Bazzite is not officially maintained by the Millennium developers, please post any Bazzite-specific installation questions, issues, or feedback here instead of opening new issues on the main repository.

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How It Works on Bazzite

Bazzite locks /usr as read-only and runs the 64-bit Steam client inside the SteamRT3 container. To work cleanly with Bazzite's atomic architecture without unlocking the root filesystem:

• systemd-sysext Overlay: Places the official linux-x86_64 release files into /var/lib/extensions/millennium/usr/lib/millennium/ and overlays them onto /usr/lib/millennium/ in memory.
• Automatic OS Update Sync: Installs a lightweight systemd boot service (millennium-sysext-sync.service) that keeps the extension's ID and VERSION_ID synced with /etc/os-release after every ujust update reboot.
• Atomic SteamRT64 Hook: Copies libmillennium_bootstrap_x64.so and libmillennium_hhx64.so into ~/.local/share/Steam/steamrt64/ and clears stale CEF htmlcache so Millennium initializes on the first launch.

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Installation & Updating

Repository & source script: https://github.com/JankyMouse/millennium-bazzite

Run the installer script to perform a fresh install or update to the latest official Millennium release:

curl -fsSL https://raw.githubusercontent.com/JankyMouse/millennium-bazzite/main/install_millennium_bazzite_64bit.sh -o install_millennium_bazzite.sh
chmod +x install_millennium_bazzite.sh
./install_millennium_bazzite.sh

1. Enter your sudo password when prompted.
2. Launch Steam once the script completes.
3. Open Steam → Settings → Millennium to configure your themes and plugins.

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Uninstalling

To remove Millennium and revert Steam to stock:

killall -9 steam 2>/dev/null || true
sudo systemctl disable --now millennium-sysext-sync.service
sudo rm -f /etc/systemd/system/millennium-sysext-sync.service
sudo systemctl daemon-reload
sudo systemd-sysext unmerge
sudo rm -rf /var/lib/extensions/millennium
rm -f ~/.local/share/Steam/steamrt64/libXtst.so.6 ~/.local/share/Steam/steamrt64/libmillennium_hhx64.so