Since starting the Session Inspector module I have been busy adding features to improve how the module functions.

One of these additions is the module now being able to retrieve and store the browser that the user is current using to access the session (also known as user agent string). This just uses a hookuserlogin() hook and stores the browser using the standard session storage system built into Drupal. This browser string is then pulled out of the session metadata and presented to the user in the session inspector interface.

Read more here: https://www.hashbangcode.com/article/drupal-9-adding-custom-plugins-session-inspector-module