Option 1

Simply Download this PB2Launcher-1.deb package and install it (do not select "Open with Software Install", chose "Select File" when prompted instead. In else case Software Install application will show "Failed to install file: not supported" message).

Note: Ubuntu seem to have issue where it won't be able to install .deb package without Internet access. For this case you can download .deb file and try option 2.

Option 2

This method would work if installation needs to be done on systems without Internet access.
Download .deb file from option 1 and save it somewhere, for example at /home/eric/Desktop/PB2Launcher-1.deb (this path will be used in command below)

Copy and paste following command into your Terminal application:

sudo dpkg -i "/home/eric/Desktop/PB2Launcher-1.deb"

This command will also require you to enter your operating system user password (not related to this website).
After that, Plazma Burst 2 icon should appear in your applications.

If you chose to install Plazma Burst 2 using method above, you can also delete Plazma Burst 2 by executing this in Terminal later:

sudo apt-get purge --auto-remove pb2launcher

Notes

Game is installed to /usr/share/PB2Launcher, everything else is here as well. It basically launches Standalone Flash Player that was download from adobe.com with help of web.archive.org, but also enables authentification that is completely optional. It means you can pretty much use any else Standalone Flash Player instead one that is bundled with game.

Make sure you use not your account password, but password for multiplayer access that can be taken from Edit Profile page (though both should work). Launcher does not report login & password mismatch.

If there is no Internet connection - launcher will skip authentification and will go straight into the game.

Game was tested to work with Ubuntu 20.10