An MC6 remote will work out of the box.
I use one with new boxes where I dont yet have the remote.config files.
You can add extra keys using kodi key mapper.
if you have it the remote config file goes either into the root of the sd card or ‘configfiles’
The modded files from Kodi key mapper end up in ‘userdata/keymaps’
To see these location I use windows explorer. Use a command like this in search bar.
\\192.168.0.12 (box ip addy found in CE setup )
I have new installed Codeelec (generic) and noticed that the IR remote from WETEK Hub worked the same, although I did not install any remote config files.
That means for me that there is something like default Kodi remote code somewhere. But where?
I set up my remote control (adaptive) and one of the predefined codes worked. (This also indicates that somewhere Kodi default remote configuration exists).
I asked where some time back. Told I think embedded into code.
Easiest if you have a remote that works is to add missing keys using Kodi keymap editor from Kodi repo in CE.