We need to consider few facts if we want to install zimbra properly on Ubuntu 20.04LTS
Zimbra Migrate from CentOS to Ubuntu
Zextras: How to Download, and Install Zextras Carbonio CE on Ubuntu 20.04 (includes dnsmasq configuration) - The Blog of Jorge de la Cruz
Install Zimbra on Ubuntu 20.04 Step by Step - inGuide
Secure Private Business Email & Collaboration, Open Source
Install Zimbra 8.8 on Ubuntu 20.04, 18.04, 16.04
Zextras: How to Download, and Install Zextras Carbonio CE on Ubuntu 20.04 (includes dnsmasq configuration) - The Blog of Jorge de la Cruz
How to install Carbonio CE on Ubuntu, Imron Rosyadi posted on the topic
Preparation Before Install Zimbra 8.8.15 in Ubuntu 20.04 (Part 1)
INTALIO - ZIMBRA 9 and 10 OSE