yes Circular, it is a font problem. I don't understand why the text is showned well on Windows and not on Linux.
In the game, the instructions are showned using the class TGuiTextArea. In TGuiTextArea.Create(...) an TBGRATextEffectFontRenderer associated with TBGRABitmap.TextRect() draw the text with the appropriate font on a TBGRABitmap, then convert it to opengl texture.
After few search, I found perhaps the issue:
In unit 'u_SpriteDefinition', line 543 there was:
// child 1: TGuiTextArea to show the instructions in the appropriate language
FTextArea := TGuiTextArea.Create( StrRes[10,FCurrentCountry], 25, 25, Width-50, Height-50,
GuiFont('', 17, [], BGRA(200,200,200), BGRA(0,0,0), 3,
BGRA(0,0,0), 1, 1, 7), taCenter, tlCenter);
In the Font definition, there is no name specified. I added 'Arial':
// child 1: TGuiTextArea to show the instructions in the appropriate language
FTextArea := TGuiTextArea.Create( StrRes[10,FCurrentCountry], 25, 25, Width-50, Height-50,
GuiFont('Arial', 17, [], BGRA(200,200,200), BGRA(0,0,0), 3,
BGRA(0,0,0), 1, 1, 7), taCenter, tlCenter);
Same with the country's panel, unit 'u_screen_title', line 151.
I updated the code in the previous link.
I hope...