Issue: "Bad serial number given in setup".

First.

To create a prefix for the game launch it.

Second.

The installation and configuration script 33910_install.vdf, which is located in the root directory of the game, every time the game starts, it erases (!) the key entry (hexadecimal value) from the Windows registry (prefix), which leads to an error "Bad serial number given in setup". You must prevent the script from running or reading: sudo chmod 000 '/home/$USER/.local/share/Steam/steamapps/common/Arma 2/33910_install.vdf'

Third.

You must generate a special value from the game key and write it to the Windows registry: echo AAAA-BBBBB-CCCCC-DDDDD-FFFFF | perl -ne 's/-//g; tr/IO/10/; for $i (0..2) { $res = 0; for $j (0..7) { $res += index("0123456789ABCDEFGHJKLMNPRSTVWXYZ", substr($_, $i * 8 + $j, 1)) << (5 * $j); }; printf("%010x", $res); }; print("\n");'

Fourth.

The output should be 15 pairs of characters (hexadecimal value), which will be the required key for the Windows registry. Now you need to add received value (15 pairs of characters) to the prefix Registry file. He is here: /home/$USER/.local/share/Steam/steamapps/compatdata/33910/pfx/system.reg In the file you need to find the line: [Software\Wow6432Node\bohemia interactive studio\arma 2]. Next to this line find the line with the name "key"=hex:. Write your received value (15 pairs of characters) in this line: "key"=hex:ff,ff,ff,ff,ff,ff,ff,ff,ff,ff,ff,ff,ff,ff,ff. Save your changes. Now the game will run without problems.