Is there any way to collect the browser type (Chrome, IE, Safari...) from the IP? Thank you!
From the IP, surely not. All the more as the IP address is not even linked to the visitor's device but to their gateway or internet box.
But the form fillout or web page visit activities, for instance, do collect the user agent:
Thank you! Is there a way to extract that data?
It's available in an Activity Log API extract.
But really, Marketo is not the ideal place to query browser-technographics, because it is centered on associated (non-anonymous) web sessions. You should use another analytics tool (Clicky, for example) for this, unless you're only interested in sessions associated w/converted leads.
Retrieving data ...