There is no such option (as I know). But you can enable masking IP addresses. In such case, last part of IP address will be set as 0. You should use as well as user tag some local ID, note username and from RODO side you should be safe 🙂 Sessions older than 35 days are deleted automatically.
You can't delete user sessions as this would require to recalculate all reports, problems (affected users) etc.
But in order to full fill data privacy, Dynatrace is providing a service to make user sessions anonymous https://www.dynatrace.com/support/help/extend-dynatrace/dynatrace-api/environment-api/anonymization/