tf91 I don't use LDAP for my accounts, however, in point 1 of my process I mentioned that you should NOT creathttps://community.grommunio.com/d/1444-suchfunktion-in-webapp-deskapp-mit-fehlermeldunge the Organisation, Domain or Users, as the database imports to your new server (items 11-13 - only use 12 if you are using Grommunio Files) will do all this as per your existing (old) server.
Looking back at my post and just to make sure this is not misinterpreted, I should have mentioned that the bold text in the various points, should be considered as a single line, not as 1 or more as it displays. ie in Item 6 you should highlight all the text from 'mysql' right through to (and including) 'done' as this is just one command sequence, it is a long command, hence my suggestion to copy and paste it. Also the 'root@192.168.xxx.xxx' bits in item 7 & 8 should be replaced with the account and IP address of your 'root' user on the new server.
Hope your second/third test go a little better. The whole above process should be performed while logged in as the default 'root' user (on both servers) otherwise you might come across permissions errors during the export process.
In item 9 I originally had chown -Rf grommunio:gromox /var/lib/gromox/user, but found that following the 11/23 new appliance ISO's that Grommunnio couldn't find my user directories after I had migrated the data. It seems there had been a slight change to the permissions in the appliance ISO and I had to set the permissions one directory higher. I built a fresh VM to check this, from the same appliance ISO, and using WinSCP found the permissions were different to my previous versions, so modified item 9 to its current form. Once I had made this change I have not had any other issues in the roughly 10 migrations I have done since with the above process.
Hope the above helps.