If you ever tried to play the bronze age mod on Linux you may have run into a bug where the game would freeze during the initial load screen. I had the same problem, but I found a way to get it to run. This post is intended as a documentation of my steps. They may or may not work for you.

1. Download Imperator: Rome from Steam
2. Subscribe to the bronze age mod on the steam workshop
3. Start Imperator: Rome and enable the mod in the paradox launcher. Close the launcher. You can try to start the game, but it will probably freeze.
4. Right click on Imperator: Rome and in properties, enable "Force the use of a specific steam play compatibility tool". Select Proton 5.0-9. Wait for Steam to download the Windows version. If you try to start Imperator: Rome now, it will try to install the paradox launcher. However, the launcher always errors out before finishing the installation, preventing you from launching the game.
5. Go to home/user/Documents/Paradox Interactive. If there is a Impetaror directory, delete it. Then create a soft link to home/user/.local/share/Paradox Interactive/Imperator. This way, the linux and windows versions of Imperator: Rome share the same config directory with the same mods installed. Since we already installed the bronze age mod on the linux version through the workshop, it is now also installed on the windows version.
6. In Steam, click "ADD A GAME" and add <steamlibrary>/steamapps/common/ImperatorRome/binaries/imperator.exe.

If you now launch imperator.exe through steam, the game should load with the mod installed.
It seems like cloud sync for save games and multiplayer is broken though, since the paradox launcher isn't installed.