no /etc/default/portmap file in ubuntu 20.04

My computer running Pop!_OS 20.04 (basically Ubuntu 20.04 with some additions) doesn't have a portmap file to resolve port numbers to service names. I did a

sudo apt install portmap

which installed a port mapper, but still, there is no corresponding file. Therefore, I cannot get service names when I run netstat.

How can I add, fill, and otherwise edit a portmap file? Or is there some other system in 20.04?

Thank you for your kind assistance,

M