For our record, fonts can be selected for the keyboard layout and for display where applicable. In the .kps file, click on the Keyboards tab on the left and then look to the right panel to see two dropdown menus to choose the font(s).
If there’s a font we think will be used by more than one keyboard, we strongly encourage it be added to the “shared” folder so it doesn’t have to be in multiple locations. Also, we do try to update the “shared” fonts when there are new versions of fonts. I don’t go trolling through the keyboards to see which versions of fonts are in there.
I see sil_tchad also includes that font so maybe it would be worth me adding it to shared. Then I’ll let you update the keyboard to use it the next time you update the keyboards. Are there other Africa subsets you want there?