Hello, in the past years I have purchased and used the ISPConfig manual to create (Apache based) ISPConfig managed multi-server setups. I have perfectly working "clusters" with ISPConfig "orchestrated" web server, DB server, mail server and so on. Now, I have to upgrade those clusters, because some of them are still Ubuntu 18.04 LTS. However, every time I upgrade the O.S. , ISPConfig stops working. The Ubuntu "per se" works perfectly, but ISPConfig totally breaks. Now, I am kind of prepared to the fact that I have to manually upgrade RoundCube and PHPMyAdmin, but I have no idea about how to upgrade ISPConfig in a way that the admin still works, that the changes I apply in the admin actually go into effect (and don't stick "forever"). I have searched Google and this forum for a solution for this, but there's only 1 thread, it's old, not really conclusive and it's about a single machine ISPConfig only. Any kind soul who has done this, could please give me some pointers, possibily some step by step process? Thanks in advance.