Glasswire is a great free app to view data usage but it is not available for Linux. You can use these commands to install a CLI based alternative in Ubuntu, Linux Mint, MX Linux and other Debian based systems.
## Install nethogs
sudo apt install nethogs
## You can use nethog with total bandwidth monitored per MB since it started with:
sudo nethogs -v 3
## SOURCE: Linux: per-application traffic monitoring (not nethogs)