Migrate Redmine 3.4.4 on Ubuntu 18.04 to Redmine 4.0.6 on Ubuntu 20.04
I have a VM running Redmine 3.4.4 on Ubuntu 18.04. It was installed via the redmine and redmine-pgsql packages. I wanted to upgrade Ubuntu to 20.04 but the upgrade fails because of redmine and/or ruby. Therefore I am thinking to set up a new VM with Ubuntu 20.04, install redmine there and just migrate the data.
How can I do this? What needs to be done?
The only tutorials that google could find me where years old. I have some doubts on how up-to-date they are.