All the software I could find that does this is broken on macOS Sierra and will probably break again in the future, so I need a solution to set the system volume in the same increments as the volume keys without needing a 3rd party app running.
If my understanding is correct, keyboards with generic media controls work without software, if I could rebind my PrintScr and Scroll Lock keys as volume up/down that would be ideal.
(I'm using a fullsize Majestouch 2 with ANSI layout.)
If that isn't possible, any Service or other Workaround is welcome. I can actually work without the bezel as long as the increments are the same.
Karabiner was one of the apps I used before, it doesn't work either and isn't likely to be fixed soon: macOS (10.12) compatibility #660
Best Answer
Karabiner has options that let you use the Function keys (with or without ‘fn’) on external non-Apple keyboards just like the special function keys on Apple keyboards. This means pressing F11 and F12 (‘fn’ depends on your options shown in the screenshot) to decrease and increase volume. The HUD shows as usual, and F10 works for mute too.
I am yet to see Karabiner fail to function due to an OS update, even day-one beta OS updates seem no trouble for these ‘standard’ features of the app (there's more customisable functionality which may have problems from OS updates but are fixed swiftly).