This is tricky. The only way to get proper MCE keyboard handling or longpress support for remotes is to disable eventlircd processing (for MCE keyboard you also have to enable the mce_kbd protocol via ir-keytable/rc_keymaps).
You can do that by creating an empty udev rule file (remove it to restore normal behaviour)
The drawback is that then several buttons, most importantly the OK button, no longer work - kodi doesn't support OK etc keys on a keyboard. You can fix that by doing key remapping via a hwdb.d file, search the forum for examples if you're feeling brave.
so long,
Hias