User research doesn't have to be loads of time, but you do have to know how to do it well. It is focused on understanding the problems users are facing. Something as simple as 15 minute calls with users/potential users can help you to gather data.
Usability testing 101 by the Neilson Norman Group
Asking good user interview questions by NCVO and Neontribe
5 ways to ask the perfect question, by Jeff Haden
Ways to involve users remotely by Joe Roberson
How to Set Up a User Research Framework by Nikki Anderson