So you not install directadmin in a clean debian installation but in customized installation? Because if you need su seems the installation is not the default as the directadmin require.It seems that the problem that causes errors like chown: invalid user: ‘diradmin:diradmin’ is caused Debian 10 now handles paths.
The fix seems to be to execute command:
After that I managed to install DA on Debian 10.1
However I got this at the end of installation:
"Got signal 13 during installation!"
and the install script did not exit and I had to use ctrl-c to get back to shell.
I recommended to do just the default debian 10 installation and then install directadmin. They work fine.