The most convenient way to install HotA on Linux involves Heroic Games Launcher program. It allows you to install HotA using both GOG and the standard installer (you can choose the method that is more convenient for you).
Heroic Games Launcher
Download and install the Heroic Games Launcher from the official website or from your distribution’s repository:
https://heroicgameslauncher.comLaunch the Heroic Games Launcher.
Installing the GOG version
Click Login in → GOG LOGIN → log in to your GOG account.
Click Library.
Find and install Heroes of Might and Magic III: Horn of the Abyss.
Launch the game.
Installing the standard version
In the Library section, click ADD GAME.
Specify the name (e.g., HotA).
Click RUN INSTALLER FIRST.
Select the path to the original game’s installer file (.exe).
Complete the original game installation using the setup wizard that appears.
After installing the original game:
Click RUN INSTALLER FIRST again.
Select the path to the HotA installer file (.exe).
Install HotA into the same folder where the original game is installed.
After installing HotA:
Click Select Executable and specify the path to h3hota HD.exe inside the game’s installation folder.
Click FINISH.
Launch the game.
Additional Notes
Using the ADD GAME button, you can create shortcuts to launch editors (e.g., the map editor).
To do this, in the Select Executable item, specify the path to the corresponding editor’s .exe file.