mjhjmtu

I've recently switched from macOS to Fedora, on macOS I used a tool called Karabiner Elements to map the key combinations

Ctrl+ö to [
Ctrl+ä to ]
Alt+ö to
Alt+ä to

I'm aware of a similar question here:

• Mapping key combination with xmodmap

and I've tried to adjust that solution to my case. So far I've got the 3 files

.xkb/types/mytypes:

partial xkb_types "lock_level2" 
 Virtual_modifiers Lock;
 type "Lock_LEVEL2" 
 modifiers= Lock;
 map[Lock]= Level2;
 level_name[Level1]= "Base";
 level_name[Level2]= "Lock";
 ;
;

partial xkb_types "alt_level2" 
 Virtual_modifiers Alt;
 type "ALT_LEVEL2" 
 modifiers= Alt;
 map[Alt]= Level2;
 level_name[Level1]= "Base";
 level_name[Level2]= "Alt";
 ;
;

.xkb/symbols/mysymbols:

partial modifier_keys
xkb_symbols "Lock_brackets" 
 key <AC10> 
 type[Group1] = "LOCK_LEVEL2",
 symbols[Group1] = [ Odiaeresis, bracketleft ]
 ;
 key <AC11> 
 type[Group1] = "LOCK_LEVEL2",
 symbols[Group1] = [ Adiaeresis, bracketright ]
 ;
;

partial modifier_keys
xkb_symbols "alt_brackets" 
 key <AC10> 
 type[Group1] = "ALT_LEVEL2",
 symbols[Group1] = [ Odiaeresis, braceleft ]
 ;
 key <AC11> 
 type[Group1] = "ALT_LEVEL2",
 symbols[Group1] = [ Adiaeresis, braceright ]
 ;
;

.xkb/keymap/mykdb:

xkb_keymap 
 xkb_keycodes include "evdev+aliases(qwerty)" ;
 xkb_types include "complete+mytypes(lock_level2)+mytypes(alt_level2)" ;
 xkb_compat include "complete" ;
 xkb_symbols include "pc+de+inet(evdev)+mysymbols(lock_brackets)+mysymbols(alt_brackets)" ;
 xkb_geometry include "pc(pc105)" ;
;

then running xkbcomp -I$HOME/.xkb ~/.xkb/keymap/mykbd $DISPLAY.

But this doesn't seem to work for the Alt and Control modifiers, but does work
when I use Shift (instead of Control) and then it only works in Sublime and Firefox but not in Gnome and the Terminal.

So I'm wondering what's wrong with the current configuration and how I can set the mapping system-wide for all apps.