I would suggest using open source Return to the Roots package to play Settlers 2 Gold on Linux. You can download it from here. You should not forget to copy your original Settlers 2 Gold folder into share/s25rttr/S2 directory after you extract the downloaded archive. Also do not forget to make bin/rttr.sh file executable. That is the file you should run to play the game. :)

The "Return To The Roots" does not support any campaign!
It's better to install S2 Gold as it is!

I wrote an article to install/play Settlers 2 Gold in Linux (Debian/Ubuntu)

"Run Settlers 2 Gold in Linux" article:
http -> idx.shrt.ws/run-settlers-2-gold-in-linux.141.en.html

Step by step on Arch Linux (this uses the provided dosbox config files, contrary to the post above, but otherwise based on t):

1. Download the Windows version of Settlers 2 from your account and put it in its own directory.
2. Install innosetup, timidity++, soundfont-fluid, dosbox. Run
`innosetup setup_settlers2_gold_2.0.0.14.exe`

3. This will create an `app` and a `tmp` subfolder. You can delete the `tmp` one.
4. Open `app/dosboxSettlers2.conf`, search for the `[midi]` section, replace `config=` with `midiconfig=128:0`
5. Edit `/etc/timidity++/timidity.cfg` and add `soundfont /usr/share/soundfonts/FluidR3_GM2-2.sf2` to the file.
6. Run timidity as a Daemon: `timidity -iA` (I wouldn't bother setting it up to autostart, if you only use it for this game)
7. `cd app/DOSBOX` and run `dosbox -conf ../dosboxSettlers2.conf -conf ../dosboxSettlers2_single.conf`

After all these years I only now figure out that this game supports Midi,......

On Linux I use Fluidsynth to make Midi play in games, however this has only worked through Wine for me, native DOSBox didn't work, not that it should matter all too much. DOSBox through wine runs perfectly fine as well! This is how I made it work with Heroic Games Launcher assuming that launcher is installed as well as Fluidsynth and some soundfont (soundfont-fluid eg.):
1- In Heroic Games Launcher install the game normally (If native dosbox is not installed, it will launch the game via the bundled Windows-version of DOSBox).
2- Create two shell scripts to auto launch and auto close fluidsynth:
Start_Midi_Server.sh:
> #/bin/sh
> fluidsynth -l -s -i -apipewire /usr/share/soundfonts/FluidR3_GM.sf2 &
>
(Note: if you don't pipewire, select alsa or pulse, be sure the path to your soundfont above is correct!)

Stop_Midi_Server.sh:
> #/bin/sh
> pkill fluidsynth
>
3- Go to Game's settings in Heroic, Advanced, and select both scripts (be also sure that they have execute right, otherwise those scripts won't launch)

That's pretty much it. You can reuse the scripts for other games with MIDI tracks as well. If you encounter them.

Alternatively if you don't want to create custom scripts, you can also use QSynth, which has to be started and closed manually when you want to game. Make sure that it is also configured properly by at least selecting the soundfont you want:
- Launch QSynth->Settings->Soundfonts->Open and select the soundfont you prefer



EDIT: After reading this blogpost (https://www.grois.info/posts/2023-02/2023-02-02-dosbox-with-midi-on-the-steam-deck.xhtml) I came to realize that it is apparently possible to play MIDI through native DOSBox, you just needed to install DOSBox-Staging instead of old DOSBox v0.74. In its config file you'd only have to specify the path to a soundfont file and it will do the rest. Heroic Game Launcher in its current state will launch native DOSBox if installed.