Please note, Plesk has supported the version of Mailman provided by OS vendor by default.
The Mailman 3 is shipped by default on Ubuntu 18 and Debian 10.
Please keep voting if this request is still actual for you.
An error occurred while saving the commentMichael Struller commented
on Ubuntu 18.04 the Mailman 2.* will install from plesk.
In Ubuntu we have an Paket mailman v 2.1.26
and an Paket Mailman3.
On command line install-component mailman3 will work?