Hey Juan.
There are 2 important behaviors here:
a) Checking Users that have connected to the environment
b) Checking if users have accessed (read) records.
The first point, on Power Platform Admin Center there are some interesting reports: Active users by client, active users by entities, Active Dynamics 365 Customer Engagement Plan Users by Application.
For the second point (tracking if users read a specific set of record), you will need to enable Auditing, as described on
Regards,
