Doomsday Engine

Hi, I'm trying to run Doomsday Engine on some old MacOSX 10.6 systems (because why not), but it all ends with error of $subject.
Even thought 1.14.x (and previous versions) should be supported on MacOSX 10.6.x it seems not to work on iMacs with ATI X1600 running macosx 10.6.
(I've also tried installing previous releases 1.10.x -> 1.14.x but they all end up with the same error.)

I see there's a similar issue that has been reported 4 years ago, same error message, but different OS and Graphics card (Windows & Intel)
https://tracker.dengine.net/issues/1977, and this issue was also fixed in 1.15.4, but this version already
The Macs I've tested on are is various iMacs (intel-based) with ATI X1600 graphics card (OpenGL is 2.0)
So all fits well with the minimum requirements.

Unfortunately Google won't point me to an solution for getting it started, and I can't find any bug/problem or forum post that hints on what could be wrong.
(Attaching full output from -vvv if that could be useful, btw I also tested added -nofsaa from #1977 too)

Most of the MacOSX versions tested are downloads from sourceforge.net and are named doomsday_1.<version>_mac10_6.dmg

I realise this is not an important issue/bug to solve, but if I could get hints on how to workaround this issue (without upgrading OS, as these old Mac doesn't support more modern MacOSX) I'd be grateful :)

The error message of interest:

Executable: Doomsday Engine 1.14.3 (Stable 64-bit #1230) May 15 2014 09:43:49
Command line options:
  0: ../Doomsday.app/Contents/MacOS/Doomsday
  1: -vdmap
  2: /Applications/Doomsday Engine.app/Contents/Doomsday.app/Contents/Resources
  3: }Data/
  4: -vdmap
  5: /Applications/Doomsday Engine.app/Contents/Resources/../Doomsday.app/Contents/
     DengPlugins/doom.bundle/Contents/Resources/
  6: }Data/jDoom/
  7: -vdmap
  8: /Applications/Doomsday Engine.app/Contents/Resources/../Doomsday.app/Contents/
     DengPlugins/heretic.bundle/Contents/Resources/
  9: }Data/jHeretic/
  10: -vdmap
  11: /Applications/Doomsday Engine.app/Contents/Resources/../Doomsday.app/Contents/
      DengPlugins/hexen.bundle/Contents/Resources/
  12: }Data/jHexen/
  13: -basedir
  14: /Applications/Doomsday Engine.app/Contents/Doomsday.app/Contents/Resources/
  15: -sfxchan
  16: 16
  17: -notexcomp
  18: -game
  19: heretic
  20: -iwad
  21: /Applications/Doomsday/Heretic.wad
  22: -wnd
  23: -nofsaa
  24: -vvv
  25: -userdir
  26: /Users/DEuser/Library/Application Support/Doomsday Engine/runtime/
RenderSystem: Loading shader definitions from read-only archive entry "data/renderer.pack/
              shaders.dei" [path "/data/doomsday.pk3/data/renderer.pack/shaders.dei"]
              from archive in read-only "(basedir)/doomsday.pk3" 

[...]

Canvas: Received first show event, scheduling GL ready notification
Recycling 5485 allocations/instances
GLFramebuffer: Required GL_ARB_framebuffer_object is missing!
^ : Reconfiguring framebuffer: (1008, 630) ms:1
^ > GLTarget: Creating FBO 1
^ : FBO 1: glTex 1 (level 0) => attachment 0
^ : FBO 1: glTex 2 (level 0) => attachment 1
GLFramebuffer: Texture-based framebuffer failed: [ConfigError] (GLTarget::validate)
                                                 Unsupported
Trying fallback without depth/stencil texture
^ > GLTarget: Creating FBO 1
^ : FBO 1: glTex 1 (level 0) => attachment 0
^ : FBO 1: depth+stencil renderbuffer (1008, 630)
(GLTarget::validate) Unsupported
Dir: Changing current directory to "/Users/DEuser/Library/Application Support/Doomsday
     Engine/runtime/" succeeded
Application terminated due to exception:
(GLTarget::validate) Unsupported

Restoring original display mode due to shutdown
DisplayMode: Requested mode is the same as current, ignoring request

Tnx