The feature "Protected Login" does not increase the security of a login in any form whatsoever, as the term may suggest.
First of all, this feature is only relevant if you are using a database on the Enterprise Server. In fact, it is only useful if the administrator allows you access to an entry, but you are not permitted to see or edit the password yourself.
In this case, if you want to log on to a website, it is possible using the "Protected Login" feature only. This means that you can log in to the given URL, but cannot see the password of the entry.
Since browsers such as Chrome or Firefox cannot be controlled by third-party applications such as Password Depot, Internet Explorer is always used for this purpose. Please note, that this is always the case regardless of your global browser settings (Edit -> Options -> Browsers -> Default browser) or the browser settings of individual entries (Password -> Properties -> Additional -> Preferred browser).
To use this feature, Internet Explorer must be installed on your device.