The question about how to see the ROS output is not really answered for me. I tried different commands, but none of them are satisfying.
snap logs <snap_name>.<app_name>
-> Does not give me any output.
systemctl status -l snap.<snap_name>.<app_name>
-> On Ubuntu 18 Desktop, this gives me some of the latest outputs. But on Ubuntu Core, besides the information about the service, this does not show me the output streams from ROS.
sudo journalctl -fu snap.<snap_name>.<app_name>
-> This does more or less what it should, except that the order of the output is not correct anymore. The log timestamp does not match the ROS timestamp.