[schrackin]

Your user is not member of video nor audio (see useradd on the first page)

uid=1000(dni) gid=1000(dni) groups=1000(dni),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),110(lxd),115(lpadmin),116(sambashare)

 now dni is part of the required groups, but the problem still persists: 
dni@ubi- htpc :~$ groups
dni adm dialout cdrom sudo audio dip video plugdev users input lxd lpadmin sambashare
dni@ubi-htpc:~$ groups kodi
kodi : kodi dialout cdrom audio dip video plugdev users input

But as far as is can tell kodi application is running by kodi user, not by dni. Could you please tell me what should I check next to get proper audio pass-through?