Create,list and delete a system or normal group and add a user to it on Ubuntu

list all members of a group

sudo apt install members
members <groupname>

https://www.cyberciti.biz/faq/linux-list-all-members-of-a-group/


delete a group
sudo groupdel <groupname>

https://www.techonthenet.com/linux/sysadmin/ubuntu/remove_group_16_04.php

create a system group
sudo addgroup --system <groupname>

add a user to the group
sudo adduser $USER/<any_username> <groupname>
(or)
sudo gpasswd -a $USER docker

https://github.com/docker/docker-snap/issues/1

Ref: Both in UI and CLI